Griula, Cavern Queen

Ambush (You may cast this card at any time you
could cast an instant. If you do, return it to your hand
at the beginning of your upkeep)
Whenever you cast a creature, if it isn't your main phase, draw a card.
She dwells in the deep caves under the sea, connected through tunnels to lakes on the mainland. None
resurface after diving into those lakes.