
Auras attached to permanents you control have umbra armor. (If an enchanted permanent you control would be destroyed, instead remove all damage from it and destroy an Aura attached to it.)
Umbra Mystic has 2 printings, first in Rise of the Eldrazi (2010). EDHREC ranks it #4,405 among Commander cards. It appears most in Light-Paws, Emperor's Voice decks (5,051 on EDHREC). 1 public deck on TCG runs it. It has 15 official rulings.
Deck counts from EDHREC.
Cards that show up in the same decks on EDHREC.