Warren Pilferers [Modern Masters] Dominaria Promos put a -1/-1 counter on

put a -1/-1 counter on it

then sacrifice it unless you pay its upkeep cost for each age counter on it

This ability can't cause the total number of +1/+0 counters on Clockwork Avian to be greater than four

shuffle your library

Warren Pilferers [Modern Masters] Dominaria Promos put a -1/-1 counter onSet: Modern Masters Type: Creature Goblin Rogue Rarity: Common Cost: {4}{B} When Warren Pilferers enters the battlefield, return target creature card from your graveyard to your hand. If that card is a Goblin card, Warren Pilferers gains haste until end of turn. "What do they need all this stuff for? They're dead. We're alive. Simple enough."