Mammoth Umbra is a common Enchantment — Aura card from Ultimate Masters (UMA), collector number 24. Current market price: $0.29 (foil $0.28), TCGplayer market prices via Scryfall.
Enchant creature Enchanted creature gets +3/+3 and has vigilance. Umbra armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.)