Swarmborn Giant is a uncommon Creature — Giant card from Journey into Nyx (JOU), collector number 144. Current market price: $0.07 (foil $0.33), TCGplayer market prices via Scryfall.
When you're dealt combat damage, sacrifice this creature. {4}{G}{G}: Monstrosity 2. (If this creature isn't monstrous, put two +1/+1 counters on it and it becomes monstrous.) As long as this creature is monstrous, it has reach.