Burning-Tree Emissary

Priest of Urabrask

When this creature enters, add {R}{R}{R}.

Ardent Electromancer

When this creature enters, add {R} for each creature in your party. (Your party consists of up to one each of Cleric, Rogue, Warrior, and Wizard.)

Akki Rockspeaker

Cloudstone Curio

Whenever a nonartifact permanent you control enters, you may return another permanent you control that shares a permanent type with it to its owner's hand.

Gamble

Search your library for a card, put that card into your hand, discard a card at random, then shuffle.

Halana, Kessig Ranger

Reach
Whenever another creature you control enters, you may pay {2}. When you do, that creature deals damage equal to its power to target creature.
Partner (You can have two commanders if both have partner.)