Skullmulcher

Devour 1 (As this enters, you may sacrifice any number of creatures. This creature enters with that many +1/+1 counters on it.)
When Skullmulcher enters, draw a card for each creature it devoured.

The List

Double Masters

Devour 1 (As this enters the battlefield, you may sacrifice any number of creatures. This creature enters the battlefield with that many +1/+1 counters on it.)
When Skullmulcher enters the battlefield, draw a card for each creature it devoured.

Shards of Alara

Devour 1 (As this comes into play, you may sacrifice any number of creatures. This creature comes into play with that many +1/+1 counters on it.)
When Skullmulcher comes into play, draw a card for each creature it devoured.

Because devour applies as Skullmulcher enters the battlefield, it can't devour creatures that enter the battlefield at the same time as it.