Witty Roastmaster

Alliance — Whenever another creature you control enters, Witty Roastmaster deals 1 damage to each opponent.

Plains

Cryptolith Rite

Creatures you control have "{T}: Add one mana of any color."

Warstorm Surge

Whenever a creature you control enters, it deals damage equal to its power to any target.

Bootleggers' Stash

Lands you control have "{T}: Create a Treasure token."

Mountain

Purphoros, God of the Forge

Indestructible
As long as your devotion to red is less than five, Purphoros isn't a creature.
Whenever another creature you control enters, Purphoros deals 2 damage to each opponent.
{2}{R}: Creatures you control get +1/+0 until end of turn.

Forest

Jinnie Fay, Jetmir's Second

If you would create one or more tokens, you may instead create that many 2/2 green Cat creature tokens with haste or that many 3/1 green Dog creature tokens with vigilance.