Treefolk Umbra is a common Enchantment — Aura card from Modern Horizons (MH1), collector number 185. Current market price: $0.17 (foil $1.11), TCGplayer market prices via Scryfall.
Enchant creature Enchanted creature gets +0/+2 and assigns combat damage equal to its toughness rather than its power. Umbra armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.)