Thalia's Lieutenant is a rare Creature — Human Soldier card from Shadows over Innistrad (SOI), collector number 43. Current market price: $0.49 (foil $3.89), TCGplayer market prices via Scryfall.
When this creature enters, put a +1/+1 counter on each other Human you control. Whenever another Human you control enters, put a +1/+1 counter on this creature.