Grothama, All-Devouring

Other creatures have "Whenever this creature attacks, you may have it fight Grothama, All-Devouring."
When Grothama leaves the battlefield, each player draws cards equal to the amount of damage dealt to Grothama this turn by sources they controlled.

Forest

Territorial Allosaurus

Kicker {2}{G} (You may pay an additional {2}{G} as you cast this spell.)
When Territorial Allosaurus enters, if it was kicked, it fights another target creature.

Neyith of the Dire Hunt

Whenever one or more creatures you control fight or become blocked, draw a card.
At the beginning of combat on your turn, you may pay {2}{R/G}. If you do, double target creature's power until end of turn. That creature must be blocked this combat if able. ({R/G} can be paid with either {R} or {G}.)

The Tarrasque

The Tarrasque has haste and ward {10} as long as it was cast.
Whenever The Tarrasque attacks, it fights target creature defending player controls.