Guildpact Informant is a common Creature — Faerie Rogue card from The List (PLST), collector number WAR-271. Current market price: $0.51, TCGplayer market prices via Scryfall.
Flying Whenever this creature deals combat damage to a player or planeswalker, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)