Darksteel Relic
:P
Okay in all seriousness I submit this answer to the Chewer:
Endurance
It blocks the attacking Chewer, kills it, survives and puts the artifact back into the library.
Is there any way for a mono black deck to get an artifact back from the graveyard?
So far I only have
Buried RuinsIll-Gotten GainsForbidden Crypt
Which is not very exciting.