Mossbridge Troll

If Mossbridge Troll would be destroyed, regenerate it.
Tap any number of untapped creatures you control other than Mossbridge Troll with total power 10 or greater: Mossbridge Troll gets +20/+20 until end of turn.

Barroom Brawl

Target creature you control fights target creature the opponent to your left controls. Then that player may copy this spell and may choose new targets for the copy.

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.

Boxing Ring

Whenever a creature enters the battlefield under your control, it fights up to one target creature you don't control with the same mana value.
{T}: Create a Treasure token. Activate only if you control a creature that fought this turn.