Merfolk Thought-Robber

Wither
When Merfolk Thought-Robber deals combat
damage to a player, that player reveals their hand.
You may choose an instant or sorcery card with
converted mana cost 2 or less revealed this way.
Exile that card. You may cast that spell from
exile, and you may spend mana as though it were
mana of any color to cast it.