Mirkwood Bats

Flying
Whenever you create or sacrifice a token, each opponent loses 1 life.

Glimmer Bairn

Sacrifice a token: Glimmer Bairn gets +2/+2 until end of turn.

Gathered Swarm — Whenever one or more tokens you control enter, put a +1/+1 counter on Cloakwood Swarmkeeper.

Whenever another creature enters, untap Midnight Guard.

Enchant creature
Enchanted creature has "{T}: Create a 1/1 green Elf Warrior creature token."

When Nest Invader enters, create a 0/1 colorless Eldrazi Spawn creature token. It has "Sacrifice this creature: Add {C}."

When Thraben Inspector enters, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")