Best of one deck with companion and fae of wishes that uses sideboard when necessary, helping you deal with different situations.

This deck is very fun to play.  I've made several versions of it and haven't quite found the perfect one yet, but this is a pretty good start.  Hopefully, it can be improved in the future when new cards get released.  This is a dual threat type of deck.  You can win by making your opponent draw from an empty library or from powerful creatures depending on their deck and your draw.  It has a lot of flexibility against most decks and is somewhat competitve. Not tier one or anything, but it can perform surprisingly well sometimes.  Consider using it for quests for killing creatures, white, blue, or black.  Alternatively you can modify the deck and remove white and just go with blue/black. 

Other versions:

My blue/black deck uses some cards that use surveil.  (Disinformation campaign, Unexplained Disappearance, whispering snitch, nightveil sprite, and thought erasure).  It is also fun to play.

Tips:

Try to cast something on turn one if possible.  Even if you have to shock yourself to do so.  Don't be afraid to use the shock lands untapped.

Cast Sage of Mysteries first and then enchantments afterwards whenever possible.

Cast your ajani pridesmates before placing tapped healing lands for an automatic +1/+1 counter.

This deck works best when you can get a decent board state setup as quickly as possible.

Use giant killer on defense against Winota when you suspect you're going up against that kind of deck (may not matter much going forward after Agent of Treachery band though)

Improvements: This deck loses badly when you fail to get things going early.  If you get behind and your opponent has a lot of tempo or is able to keep a board prescence and you're not.  If there was room I'd add Teferi Timeraveler and perhaps some unsummons or something to ensure you can get ahead of your opponent.

Weaknesses: Exiling your creatures and/or your graveyard really hurts.  Hexproof threats can be very difficult to deal with, and if you struggle with land drops and someone is using land destruction you'll probably lose.