Scaleguard Sentinels is a uncommon Creature — Human Soldier card from Dragons of Tarkir (DTK), collector number 201. Current market price: $0.10 (foil $0.17), TCGplayer market prices via Scryfall.
As an additional cost to cast this spell, you may reveal a Dragon card from your hand. This creature enters with a +1/+1 counter on it if you revealed a Dragon card or controlled a Dragon as you cast this spell.