Kroak, Swarm Caller

Swampwalk
Whenever Kroak or a frog you control deals combat damage to an opponent, you may mill 4 cards.
Whenever you mill one or more creatures, you may
pay {2}{g/u}. If you do, exile one of those creature
cards from your graveyard and create a token copy
of it under your control, except it's a 3/3 green frog creature.