Archpriest of Shadows is a rare Creature — Human Warlock card from March of the Machine Promos (PMOM), collector number 89p. Current market price: $1.17 (foil $1.26), TCGplayer market prices via Scryfall.
Backup 1 (When this creature enters, put a +1/+1 counter on target creature. If that's another creature, it gains the following abilities until end of turn.) Deathtouch Whenever this creature deals combat damage to a player or battle, return target creature card from your graveyard to the battlefield.