Bats of Dol Guldur

Corruption 5 - Bats of Dol Guldur enters the battlefield with 5 corruption counters on it.
At the beginning of your upkeep, remove a corruption counter from it and create a 2/1 black Bat creature with flying and haste.
When the last is removed, destroy all Bat creatures and sacrifice Bats of Dol Guldur.
Creatures you control get +1/+0.