Rulings

• 2016-11-08
  Spells you cast from your hand this turn will gain cascade even if Yidris leaves the battlefield.
• 2016-11-08
  If Yidris's triggered ability resolves more than once in one turn, spells you cast from your hand will gain cascade that many times. Each instance of cascade triggers separately; resolve one cascade trigger and the spell you cast from it before resolving the next cascade trigger.
• 2016-11-08
  When the cascade ability resolves, you must exile cards. The only optional part of the ability is whether or not you cast the last card exiled.
• 2016-11-08
  The cascade ability triggers when you cast the spell, meaning that it resolves before that spell. If you cast the card exiled by the cascade ability, that spell will go on the stack above the spell with cascade.
• 2016-11-08
  If a spell with cascade is countered, the cascade ability will still resolve normally.
• 2016-11-08
  You exile the cards face up. All players will be able to see them.
• 2016-11-08
  You don't have to cast the last card exiled by a cascade ability. If you choose to do so, you're casting it as a spell. It can be countered. Since it's cast from exile, Ydris's ability won't give the new spell cascade.