Impact Tremors

Whenever a creature you control enters, this enchantment deals 1 damage to each opponent.

Sol Ring

Jetmir, Nexus of Revels

Creatures you control get +1/+0 and have vigilance as long as you control three or more creatures.
Creatures you control also get +1/+0 and have trample as long as you control six or more creatures.
Creatures you control also get +1/+0 and have double strike as long as you control nine or more creatures.

Ajani's Pridemate

Whenever you gain life, put a +1/+1 counter on this creature.