Veteran Guardmouse is a common Creature — Mouse Soldier card from Bloomburrow (BLB), collector number 237. Current market price: $0.16 (foil $0.27), TCGplayer market prices via Scryfall.
Valiant — Whenever this creature becomes the target of a spell or ability you control for the first time each turn, it gets +1/+0 and gains first strike until end of turn. Scry 1. (Look at the top card of your library. You may put that card on the bottom.)