Guildpact Informant is a common Creature — Faerie Rogue card from War of the Spark (WAR), collector number 271. Current market price: $0.58, 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.)