Octopus Umbra

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.

If a spell or ability says that it would "destroy" a creature enchanted with an Aura that has umbra armor, that spell or ability is what causes the Aura to be destroyed instead. Umbra armor doesn't destroy the Aura; rather, it changes the effects of the spell or ability. On the other hand, if a spell or ability deals lethal damage to a creature enchanted with an Aura that has umbra armor, the game rules regarding lethal damage cause the Aura to be destroyed, not that spell or ability.