NOTE TO SELF: Add Court of Vantress and Hullbreaker Horror (how did I forget to put one in!), add Auton Soldier (FUN!!), Cybermen Squadron, Roaming Throne, Mirage Mirror, Irenicus's Vile Duplication, Quantum Misalignment, Mechanized Production, Reasonable Doubt, Maze of Ith, Swarmyard, Riptide Laboratory, Mystic Sanctuary, Myriad Landscape, Path of Ancestry, Timestream Navigator, Lighthouse Chronologist, Case of the Ransacked Lab, Faerie Artisans, Command Beacon, Azor's Gateway // Sanctum of the Sun, Temple of the False God, Chromatic Lantern, Cloudpost, Urza's Workshop, Urza's Saga (gets Sol Ring, Commander's Plate, and Treasure Vault), Kairi, the Swirling Sky, Mystical Tutor/Personal Tutor/etc (for finding Nanogene Conversion), Spellseeker, Dowsing Dagger // Lost Vale (to copy Dowsing Dagger // Lost Vale), Slip Out the Back, Ojer Pakpatik, Deepest Epoch, Kitesail Larcenist, Metallurgic Summonings, Eye of the Storm, Misleading Signpost, Elephant Graveyard, Luck Bobblehead...

This is my regularly updated decklist for the deck I use, so it's not a 'fully optimized' list.  That being said...

Orvar, the All-Form dictates most of how you build a deck around him... tons of targeting instants and sorceries, and lots of great permanent options to target and make copies of.  The more I've played with Orvar, the more I've realized that he's strongest when he's stealing other people's best stuff and using it against them, AND making copies of those permanents (mainly creatures) if possible.  Most of the targeting spells I'm using here are 1cc instant spells that can target any permanent (copying lands is fun!), or at least target multiple types of permanents.  The ones that only target creatures hopefully can serve numerous potential uses, or one very beneficial one (like Energy Tap).  I've also made sure to include every cheap targeting instant/sorcery that lets itself be cast twice.  Similarly, I tried to stay away from sorceries unless they provide enough extra benefits (like flashback, card draw, mana, etc.), because the options you have with an instant in hand versus a sorcery with Orvar is night and day.  I previously had up to 28 targeting instants and sorceries, and currently only have 21, but might add one or two back, depending on how the current build runs.

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First off I want to mention the illegal card in the deck, Tolarian Academy, which is being allowed by my group because this isn't really an artifact deck (18 total at the moment) for it to really go crazy with.  It still goes crazy enough at times, but not enough to be ban-worthy.  Obviously, it is a legendary land, so you can't have multiple copies in play without Mirror Gallery/etc in play as well.  But that doesn't mean it can't still be abused.  Tap it for mana, then target it to make a copy and sacrifice the original, giving you a fresh new untapped copy.  You turn an instant spell into as much mana as the Academy can tap for, which can be handy when you're drawing a massive amount of cards.  Anyway, it's banned, so if you want to use one as well, discuss it with your group.  Mine might get re-banned by my group in the future, too.  Never know.

Mirror Gallery and Sakashima of a Thousand Faces make a ton of sense in an Orvar deck that utilizes legendary cards more, but seeing as I don't own either, I decided to stay away from any legendary cards that aren't essential or high synergy, and instead just use cards like Vesuvan Duplimacy or Spark Double that create non-legendary copies, which Orvar can then copy (I would never ever make any copies of Orvar, ever... how dare I...).  This is quite handy when copying a stolen commander too    The added bonus of Sakashima and the Mirror is you can copy opponents' commanders easier (after you steal them), but if Sakashima/Mirror get removed you have to sacrifice down to only one legendary copy, making them a risky plan to bet on, unless you're ready to make a quick copy of them.

Spiketail Drakeling, Voidmage Prodigy, and Overcharged Amalgam are the only counterspell effects in the deck at the moment, for the obvious reasons of being able to copy them with Orvar and counterspells.  But I've been tempted to add a proper Counterspell, Mana Drain, etc, as well (I don't have any of the free counterspells), and may end up doing that in the near future.

Auton Soldier is an absolute must-have in the deck!  Copy Orvar, trigger myriad, the token copies are nonlegendary, then cast an instant during combat targeting one of them... assuming you have three opponents, you should be making three nonlegendary copies of Orvar... but wait, it gets better... make the Orvar you target be the Auton Soldier copy, and now you have three nonlegendary copies that each have myriad!  Cast another instant if you can, or better yet, cast one on the next turn's combat after your (myriad) myriad triggers all resolve... lol... oh the fun...

On that note, Nanogene Conversion is gnaaaarly in this deck too!  For four mana you turn all your creatures into nonlegendary copies of Orvar, then cast one spell targeting one of the Orvar copies, triggering all the other Orvars to make a copy of it.  Say you have eight creatures and Orvar, well, now you have eight copies of Orvar (plus the original).  At the end of turn, the Nanogene copies turn back into their original creatures, and you still have eight Orvar copies ready to get downright oppressive!  Cast another spell targeting a nonlegendary Orvar copy to basically double the number again... it's just not fair.

Cybermen Squadron gets out of hand quickly the more you copy it, since myriad stacks, and each copy gives the other copies another trigger, and they're 5/5's.  So if you have Cybermen and two copies in play, and attack with all three, each opponent will have 9x 5/5's coming at them.  Make another copy and they'll have 16x 5/5's attacking each of them.  It gets wonky fast.

Eldrazi Conscription might seem like an odd addition, but copying it can change things very fast.  If you cast it on your commander, expect a retaliation, due to the potential commander damage you would be setting up... so instead, target a much less threatening creature, and just hope it resolves.  Once it's in play, you can target it and put the copies on Orvar... at instant speed... in combat... +10/+10 trample... two copies could potentially remove a player if Orvar went unblocked, and three copies should be a kill.  The deck typically ramps very well, seeing as it's usually easy to make copies of land or mana dorks if needed, so being able to cast it by early/mid-game should rarely be a problem.

Body of Knowledge and Illusory Ambusher make for great targets to copy when extra blockers and card draw are needed... attack with the copies you have, strategically leaving yourself open for an attack, then copy them to use as a blocker and draw cards.  Once friends know that's what you're doing, they won't attack on the ground as often, nor block your Body of Knowledge or Ambusher.  Quite handy to have around.

Tolarian Contempt is a borderline include/exclude card for me... but once it's in play, and you make copies of it, it could be a big game swing until they are dealt with.  I have yet to play it in a game, but my gut says to not copy it until you have to, or until someone tries to remove it.  Two in play is probably the maximum before you are just begging for someone to drop a board wipe.  But if an opponent is getting out of control, having three or more copies of it in play should shut down anything based on creatures.  And if you have access to counterspells for board wipes, go ahead and make three or four copies of it... see how fast your opponent's scoop!

Vesuvan Duplimacy doesn't usually last long in play, so don't cast it unless you have Orvar in play and an instant you can copy it with if/when someone tries to remove it.  Having two or three copies of Duplimacy in play makes things get wonky fast.  Same thing with Helm of the Host on Orvar, as once you have a non-legendary copy of Orvar in play, you can make copies of it with the other Orvar(s)... so, again, don't cast it unless you can make a copy of it at instant speed, as it will be removed... it has to be, or the game gets out of control fast.  In a similar vein, Mirror Box shines in an Orvar deck, for obvious reasons, except that Orvar prevents you from having it target itself to make copies, so you'll have to find another way to copy Orvar before it lets thing get out of control.  Still, with all the other copies of creatures in play around Orvar, Mirror Box's other benefits make it worthy of having around, and having multiple of them in play is that much better, albeit better options should be available as targets to copy.

Endless Evil is another fun card with Orvar, as most of the creatures in this deck are prime targets to make copies of, either for ETB triggers or every-turn effects, etc.  Making copies of it on other creatures is even more fun.  In the event you get to play it on Orvar while Mirror Box is in play, Orvar will be a Horror and return Endless Evil to your hand if Orvar dies.

Once you've turned Azor's Gateway // Sanctum of the Sun into Azor's Gateway // Sanctum of the Sun, and after you tap it for X mana, target it to make a new copy, then the legendary rule removes the first one, and now you have an untapped new one to use, for the cost of one cheap instant/sorcery... talk about ramp!  I don't care how many cards are in your hand, you can cast it all out if you want.  On top of that, if anyone tries to remove Azor's Gateway you just target it and make a copy.  The requirement to flip it keeps building no matter which copy is there at the end to flip (now that tokens can transform), so you will eventually get it flipped if you stick with it.

Isochron Scepter and Elite Arcanist cast the copies they make, so they trigger Orvar for copies as well.  Choose your instant card wisely... then make copies of the Scepter or Arcanist with Orvar, exiling new instants to make copies of.  Rinse, repeat, abuse. 

Eldrazi Monument is a borderline include, because it doesn't provide much early/mid-game value too often... it's mostly a late-game finisher, once you have enough creatures in play to feed the sacrifices every turn.

Lier, Disciple of the Drowned is like gold with Orvar... letting you flashback instant spells any time you want is granting Orvar a lot of power!  The biggest problem with the deck is not having enough instant spells to cast, and Lier makes that problem go away.

Mind's Dilation is pretty self-explanatory... the more copies of it you have, the more free spells you get to cast out of your opponents' libraries, and you simultaneously mill them out.  Win-win!!  One copy in play can be pretty oppressive as it is, but three or four copies verges of group panic mode.

Glacial Chasm is a fun one... assuming you have an instant to copy it with, you can replace the existing one after "beginning of upkeep" triggers go on the stack, but before the new counters go on the original one (which then requires payment before responses can be made).  Being able to last a couple of turns with each copy of Glacial Chasm, they can do wonders when the game is getting dire, but you have enough life to spare and stay afloat until an answer is drawn.  This is not a mana source though... you save it until you need it.  Copying it during your upkeep, you can get two full turns of no damage for 2 life, or three turns for 6 life, which can be very much worth it if you are looking for another instant to replace it with, but have a host of imminent threats at your doorstep.

Kairi, the Swirling Sky needs to be in the deck, and will be in due time.  Having a death trigger would normally kind of suck to have to rely on in a moment of need, without a sac outlet on hand, but because Kairi is legendary, making a copy of it means one of them (the copy) gets sacrificed as soon as the copy enters play.  That means instant speed removal of nonland permanents if they cost 6cc or less, and/or instant speed removal of all tokens you don't want in play (that don't have a copied casting cost)... with the cast of one cheap instant spell.  If that wasn't enough, you can opt to mill six cards and return two instant and/or sorcery cards to hand, which lets you keep reusing the same spells out of your graveyard without having to exile them.  Copy a land, copy another permanent, copy Kairi to return the first two instants back to hand, cast one to copy a land, cast the other to copy Kairi and return the other two to hand, rinse, repeat, abuse.  And the fact you're getting a 6/6 flyer with ward 3 for 6cc is pretty strong all on its own, making it that much harder for opponents to deal with.

Torrential Gearhulk is a fun option to consider, as it will let you systematically cast each targeting instant spell in your graveyard, one by one, each targeting a Torrential Gearhulk that lets you cast the next one.  Cast the Gearhulk with three instants in your grave, then use them to make three more copies of the Gearhulk for free, and all at flash/instant speed, allowing you to quickly drop a handful of 5/6 creatures before your turn.  The question is whether or not that makes it worthy of replacing something else in the deck. 

Sakashima's Protoge should be cast without using the ETB trigger to copy a permanent.  Once in play, you can copy it and copy any new permanents that enter play; if you cast it and make it a copy of something, you can no longer make copies of new permanents with it.  This is quite useful in an Orvar deck, as there typically are not many cards that you can continually make copies of to copy new targets... usually, the card you cast ends up copying something, and then you're stuck only copying the original target.

Grinning Totem needs to go in the deck... being able to copy it, then sac the copy to search any opponent's library for a card, like a counterspell, or a board wipe, or targeted removal, at instant speed, is just too powerful... it almost puts you in God-mode once you have enough mana and card draw, especially if you know the decks you're playing against, and have an idea of who has different answers you can go grab.  Granted, you're limited to casting blue or colorless spells, but that means having access to lots of good stuff, as more often than not you'll have at least one opponent running blue, or colorless control/removal, etc, because their colors don't have easy access to it.

Memory Jar is a fun card in here too, providing you with instant access to seven more cards, which might be what you need to solve a problem.  Magus of the Jar obviously does similar, but you'll probably want to copy it just before your turn begins so that the copy loses summoning sickness right after.  Keep making copies and not using them, and you can maybe mill someone out if needed, or have access to multiple rounds on Jar action on tap.  But, if opponents have no hand size limit, you'll be helping them with multiple Jar uses at once, since the exiled cards will all go back to their hands.

Riptide Shapeshifter is another fun one to consider... sacrificing copies of it almost gives you a creature tutor on tap, and if you know your creature types in your deck, you can possibly get exactly what you want/need with one try.  The deck is heavy on Humans and Wizards, so searching for either of those is a crapshoot on what you find, but most of the other types are limited in the options in the deck, so grabbing specific creatures can certainly be done (Sphinx, Cat, and Avatar get you card draw (for cheap with the Sphinxes!), Zombie gets you a counterspell creature, Faerie steals a creature, etc).  It's not a cheap tutor overall, but it's reusable and effective, and in my experience, the deck runs heavy on land and mana sources, and ramps as well as you want it to (copy mana dorks/rocks or land, etc), so its cost shouldn't be too much of an issue as the game goes on.

Magus of the Mind requires multiple extra copies to really shine, so ideally you want to make multiple copies to use one after another, and the 3+ is an ideal minimum.  Say you have three copies ready to go, and your opponents have collectively cast three spells on one of their turns, you then follow by casting a targeting instant that makes a new copy of Magus of the Mind (for a later turn), for a total of four spells cast, and then you start sacrificing your Magus of the Mind copies...  The first one you crack will look at 4+1 cards, and let's say you get three spells to cast for free, netting you an instant to copy Magus of the Mind again (there are now two copies with summoning sickness).  Sacrifice the second copy and now you get to exile 7+1 cards, and let's say you get to cast five for free, two of which are targeting instants, which you make a third copy of Magus of the Mind, and then make a copy of a land (untapped).  Sacrifice the third and final copy, and now you get to exile 12+1 cards and maybe cast nine more for free, three of which can copy more permanents in play.  That's 17 spells cast for free from the top of your deck for a total of four blue mana (three copies activated and one instant), albeit in total it required three instant spells to get it all kicked off.  But then the next turn you have 3+ copies to abuse again, or with a Lightning Greaves or Swiftfoot Boots in play, you can go through your whole library in one turn.  But you're exiling your library away, so make sure you are building a wincon in all the madness, and don't mill yourself too thin.  It's a sneaky good card in here because it's more dangerous than people think... it's cheap to both copy and activate, and crazy powerful, all at the same time.

Decree of Silence isn't cheap to cast, but once it's in play, and you can make copies of it, you can basically counter every spell your opponents can cast... but, they will try to cast as many cheap spells as possible to get rid of it, so having targeting instant spells on tap to copy it with, with mana to cast them, should be a requirement to make it last until your next turn.  Obviously, this is a late-game piece to the puzzle.

Knowledge Pool is fun!  After you cast it, you will have the first go at casting a spell to swap with cards exiled with Knowledge Pool, snagging the best stuff first.  Start with casting cards you don't want to swap for ones you do, and if an opponent should respond with an instant spell to swap for a card as well, be ready to respond to theirs and get the next best card... it's a race to snag the best stuff first.  The instant spells you cast and exile to Knowledge Pool are mostly of little value to opponents, so they won't likely want to swap for them.  That should leave them in exile, available for you to swap with another instant spell you cast, letting you target a permanent to copy it when wanted at instant speed.  You get the best of both worlds, forcing your opponents to either cast bad cards and wait for Knowledge Pool to get destroyed, or cast good cards and swap them with worse cards, letting you then cast an instant spell in response and swap for their good card while their spell is still on the stack!  And you get to retain your instant/sorcery spell access to keep copying stuff with Orvar.  You effectively shut everyone else down, but Orvar keeps groovin.  Plus, copy it with Orvar and you get a fresh set of exiled cards to play with.  And best yet, they can't remove it by way of casting a spell, unless they are willing to let it get exiled and potentially let you cast it and remove something else in response!  Board wipes are trickier to deal with, as they can still be cast by someone else a second time, unless they are limited board wipes that you could use/abuse (like Farewell or Merciless Eviction).  But like a Wrath of God is going to be hard to avoid without a counterspell.  But if you want to cast something good, you almost need to wait until you have an instant in hand to cast afterward, in response, to swap for the first card, so there are still some limitations to the fun you get to have.  But overall, Knowledge Pool can potentially let you dictate a lot of an early-mid game with Orvar in play, if you have enough cheap instants/sorceries in hand to swap with better cards.  Later in the game, it might be too limiting to what you want to do, say if you have 20 cards in hand and 15 mana available, and want to go wild, because you can, Knowledge Pool could/will complicate things.  But the ideal way to go is to first swap for only the best must-have cards that get exiled, then be patient and steal opponents' top spells as a response to them casting them (but any opponent can do the same if they get priority to respond before you).  It makes things complicated for sure, but in Orvar's world that isn't necessarily a bad thing, so long as you stay on top of how everything is supposed to work on the stack, and work it all to your advantage.  Also, say it's mid/late-game after a successful board wipe, and an opponent starts popping off real fast... with Orvar and Knowledge Pool in play you can potentially copy Knowledge Pool as many times as possible, in an effort to exile enough cards from everyone's decks until you find an answer to stop them, like another board wipe or appropriate removal.

Inga Rune-Eyes is kinda cool when she gets copied, as her scry 3 ETB trigger will go on the stack the next time a player gets priority, except state-based actions are checked right before priority passing, where the legend rule will force one Inga to go to the grave, putting the death trigger on the stack with the ETB trigger, simultaneously, letting you choose the order.  So if you time it after a couple creatures die, you can scry 3 then draw 3.  A kicked Rite of Replication will let you get a bunch of these triggers lined up however you want, except with five of each trigger.  Fun stuff!

On that note, Rite of Replication started out in the deck and got pulled out, but it will be going back in next summer (I live in Cambodia, with my cards at home near Seattle).  The reason it came out was based on the cards that were in the deck at the time, but it's evolved a lot since then.

Since this deck casts, copies and steals creatures, amassing an army, Transcendent Message can be a quite useful draw card here... block with a bunch of untapped creatures, before damage is dealt you cast Transcendent Message and tap those creatures, plus add some more mana, and draw a bunch of cards, which can replenish your stock of instant spells to make more copies with.  Or just cast it before your turn begins, tapping out all your untapped creatures and mana sources, drawing a ton of cards without tying up any mana sources.  It's a must-have draw card for any blue decks that build up an army of creatures.

Casting Diluvian Primordial is fun, but simply having it in play is almost better, since an instant spell copying it gives you instant speed access to every instant and sorcery in every player's graveyard, including board wipes, counterspells, removal, ramp, card draw... whatever is out there.  Potentially having access to a 1cc instant speed board wipe or counterspell is pretty strong!  And getting one spell from each graveyard is crazy strong, especially if you can source more targeting spells to make more copies of permanents!

Spectral Arcanist is an intriguing option for mid/late game... since Orvar is a changeling, you'll have at least two Spirits in play, allowing you to cast a lot of instants and sorceries pretty easily, especially if you cast a cheap targeting instant to make another Arcanist.  If your opponents have enough targeting instants and sorceries in their graves, you can effectively cast them all for free, making a copy of Spectral Arcanist each time, and exiling all of them from their graveyards.

Blood Clock and Umbilicus are intriguing options, if you're building around stealing opponents' stuff, which builds up your collection of permanents, and removes theirs, it can be a quite limiting card, and copying it expedites the process, and puts pressure on them to take the life loss over return lands to their hands, pending how much life they have left.  And once lands are going back, recasting stuff gets trickier.  And if you can copy Orvar and start making 2+ copies per instant you target with, you'll have plenty of fuel to return to your hand to keep your board state way ahead of everyone else.  Noetic Scales is a similar option, as well.  Ponder it over...

Once you build enough of a board state, Storm Cauldron becomes a fun card, as the main power of an Orvar deck is in its cheap instant spells you cast to copy stuff.  So you're spending little to do a lot, and your opponents are strapped by Storm Cauldron, with you stealing all their stuff for cheap.  And if they try to get rid of Storm Cauldron, you just make a copy of it.  It's best to wait to cast it until you have a good card draw engine in play so you can fuel your hand with cheap instant spells while your opponents are stuck in the mud.

Case of the Ransacked Lab is probably a must-include... the cost reduction is not going to do much with so many instants and sorceries only costing one blue to cast, but copying it both draws you a card, but then the next time you copy it you draw even more, then even more, replenishing the targeting spells in your hand, allowing you to get drawing into your deck pretty fast and far, and for only 3cc.  The solved/unsolved part doesn't really matter too much, as most of our triggering spells are instants that we want to cast later on other turns when it will already be solved.

Roaming Throne is definitely a must-include!  Since Orvar is every creature type, it won't matter to it what creature type you choose (pick it based on what you have in play or your hand), and it will give you additional Orvar triggers, which can get wonky.  Copy Roaming Throne with an instant spell, and instead, you get two copies.  Copy it again and you get four more copies.  Copy it again and you'll get eight more copies, etc, etc.  Then copy a different permanent and... all hell starts to break loose.  Even if you only copy the Throne once (giving you the original and two copies), things can get pretty nuts when you start copying other creatures, getting four copies with each targeting instant.

Mirage Mirror is a must-include, as it can copy any artifact, creature, enchantment, or land, which you can then copy with Orvar... so whatever the best of those on the board is, you can copy it, then next turn copy something else, or maybe change it twice in one turn to copy an opponent's combo pieces...?

The One Ring doesn't need any introduction or explanation of its value, but it's worth noting that Orvar can copy it and let the legendary rule get rid of the original, effectively resetting the counters on it to zero if your life should get too low.

Ojer Pakpatiq, Deepest Epoch // Temple of Cyclical Time is another fun one, for the huge rebound benefit it provides on the front side, but making copies of it can be kind of fun too, since the copies can transform, making a copy of the land side an abusable trait.  For one, the backside isn't legendary, while the front is, and a copy won't enter with any of the counters it gets when transforming from the front side.  This means you only have to tap it for mana once to transform the token into Pakpatiq.  So if you leave the original as land and make copies of it as needed, you can consistently have a token copy of the front side in play... and not many run enough land removal to get rid of the original while transformed.  This means possibly avoiding using it for mana so you don't remove counters too fast, or at least avoid using it once it only has one counter left, maximizing the value of the token copy.

Multiclass Baldric is sneaky good, since Orvar is a changeling and is each creature type.  That doesn't mean you get the full party, but you get the lifelink, deathtouch, haste, and flying for the equipped creature, and then you can copy the Baldric and equip it for only 2 mana.  It's a pretty high-value card with Orvar, if not just for the life gain benefit, but each ability has great value in the deck.

TARDIS is also an interesting option, as Orvar counts as a Time Lord, so you can cast a 1cc instant/sorcery after attacking with TARDIS and you are nearly guaranteed to hit another instant or sorcery to target with, doubling up your efforts to copy stuff.  The only other 1cc spells are Sol Ring and Mystic Remora, and it's hard to call those a "miss".