Herald of Kozilek

Devoid (This card has no color.)
Colorless spells you cast cost {1} less to cast.

Brood Monitor

Devoid (This card has no color.)
When this creature enters, create three 1/1 colorless Eldrazi Scion creature tokens. They have "Sacrifice this token: Add {C}."

Yidris, Maelstrom Wielder

Trample
Whenever Yidris deals combat damage to a player, as you cast spells from your hand this turn, they gain cascade. (When you cast the spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)