Mephidross Stalker

Weld (Each artifact you sacrifice while casting this
spell pays for {1}.)
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 Mephidross Stalker enters the battlefield,
put X +1/+1 counters on it, then put a +1/+1
counter on it for each creature or artifact you sacrificed this turn.