Crab Umbra

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.

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 spell or ability would destroy both an Aura with umbra armor and the creature it's enchanting at the same time, umbra armor's effect will save the enchanted creature from being destroyed. Instead, the spell or ability will destroy the Aura in two different ways at the same time, but the result is the same as destroying it once.

Umbra armor's effect is applied no matter why the enchanted creature would be destroyed: because it's been dealt lethal damage, or because it's being affected by an effect that says to "destroy" it (such as Breathe Your Last). In either case, all damage is removed from the creature and the Aura is destroyed instead.

Umbra armor has no effect if the enchanted creature is put into a graveyard for any other reason, such as if it's sacrificed, if the "legend rule" applies to it, or if its toughness is 0 or less.

Umbra armor's effect is not regeneration. Specifically, if umbra armor's effect is applied, the enchanted creature does not become tapped and is not removed from combat as a result. Effects that say the enchanted creature can't be regenerated won't prevent umbra armor's effect from being applied.

When Crab Umbra's activated ability resolves, it will untap the creature Crab Umbra is enchanting at that time (regardless of what creature Crab Umbra was enchanting when the ability was activated). If Crab Umbra has left the battlefield by then, the ability will untap the creature it was enchanting at the time it left the battlefield.

Only Crab Umbra's controller (who is not necessarily the enchanted creature's controller) can activate its activated ability.