Lion Umbra

If a creature you control is enchanted with multiple Auras that have umbra armor, and the enchanted creature would be destroyed, one of those Auras is destroyed instead—but only one of them. You choose which one because you control the enchanted creature.

If a creature enchanted with an Aura that has umbra armor would be destroyed by multiple state-based actions at the same time (most likely because a creature with deathtouch has dealt damage to that creature greater than or equal to its toughness), umbra armor's effect will replace all of them and save the creature.

If a creature enchanted with an Aura that has umbra armor has indestructible, lethal damage and effects that try to destroy it simply have no effect. Umbra armor won't do anything because it won't have to.