Sabnach, the Empty One

Devour 1 (As this creature enters, you may sacrifice any number of creatures. It enters with that many +1/+1 counters on it.)

When this creature enters, you gain 2 life for each creature it devoured, then target creature gets -X/-X until end of turn, where X is the amount of life you gained.

The eldest nymphs whisper that it was once a healer
but that was long ago.