Impact Tremors

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

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Sol Ring

Gev, Scaled Scorch

Ward—Pay 2 life.
Other creatures you control enter with an additional +1/+1 counter on them for each opponent who lost life this turn.
Whenever you cast a Lizard spell, Gev, Scaled Scorch deals 1 damage to target opponent.

Goblin Bombardment

Sacrifice a creature: Goblin Bombardment deals 1 damage to any target.