Yidris, Maelstrom Wielder (Gilded Foil) - Secret Lair Drop Series (SLD)

Trample
Whenever Yidris, Maelstrom Wielder 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 exile cards on the bottom of your library in a random order.)