Bats have flapped around since Homelands, usually as small black fliers that chip away at life totals. Most Bats are cheap, evasive creatures with flying that trade in small bursts of damage and lifegain.
Zoraline, Cosmos Caller gains you life whenever a Bat attacks and can pay mana and life to reanimate a cheap permanent each time it enters or attacks, so small Bats keep coming back. Desecrated Tomb adds a flying Bat token whenever creature cards leave your graveyard, pairing neatly with that recursion. Aclazotz, Deepest Betrayal takes a more aggressive approach, forcing discards on attack and turning any discarded lands into Bat tokens. Mirkwood Bats will each opponent whenever you create or sacrifice a token.