Totem armor

Totem armor is a keyword ability that was introduced in Rise of the Eldrazi and returned in the Savage Auras deck of Planechase 2012, the Adaptive Enchantment deck in Commander 2018, and in Modern Horizons. If a permanent enchanted by an Aura with totem armor would be destroyed, the Aura is destroyed instead. If that permanent is a creature, all damage is removed from that creature. In this sense, totem armor works similarly to Regeneration.

Description
In the Rise of the Eldrazi set there are 10 aura cards with totem armor; green (4), white (3) and blue (3). In addition, the creature card Umbra Mystic can give the totem armor ability to auras.

All auras with totem armor in Rise of the Eldrazi have a two-word name, consisting of the name of an animal followed by the word 'Umbra'. The artwork of these cards (all illustrated by either Howard Lyon or Christopher Moeller) depicts a floating humanoid, surrounded by a glowing 'aura' in the color of the card and in shape of the animal the card is named after. For example, Bear Umbra depicts an elf surrounded by the glowing green figure of a bear, Hyena Umbra depicts a human surrounded by the glowing white figure of a hyena, and Eel Umbra depicts a merfolk surrounded by the glowing blue figure of an eel.

Totem-Guide Hartebeest, also from the Rise of the Eldrazi set, is a card that tutors for an aura. Although its name links it to the totem armor auras, it can tutor for any aura card, not just ones with totem armor.

Three new Umbras were printed in preconstructed decks; one white and the only multicolored one in Planechase 2012, and a blue one in Commander 2018. Estrid, the Masked also generates Aura tokens that have totem armor. Modern Horizons brought another green Umbra, with the distinction of having a new artist (Zack Stella).

Rulings

 * Totem armor's effect is mandatory. If the enchanted permanent would be destroyed, you must remove all damage from it and destroy the Aura that has totem armor instead.
 * Totem armor's effect is applied no matter why the enchanted permanent 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 Doom Blade). In either case, all damage is removed from the permanent and the Aura is destroyed instead.
 * Totem armor has no effect if the enchanted permanent is put into a graveyard for any other reason, such as if it's sacrificed, if it's legendary and another legendary permanent with the same name is on the battlefield, or if its toughness is 0 or less.
 * If a permanent you control is enchanted with multiple Auras that have totem armor, and the enchanted permanent would be destroyed, one of those Auras is destroyed instead—but only one of them. You choose which one because you control the enchanted permanent.
 * If a creature enchanted with an Aura that has totem armor is indestructible, lethal damage and effects that try to destroy it simply have no effect. Totem armor won't do anything because it won't have to.
 * If a creature enchanted with an Aura that has totem armor would be destroyed by multiple state-based actions at the same time (because it's been dealt lethal damage and been dealt damage by a source with deathtouch, for example), the totem armor's effect will replace all of them and save the creature.
 * If a spell or ability (such as Planar Cleansing) would destroy both an Aura with totem armor and the permanent it's enchanting at the same time, totem armor's effect will save the enchanted permanent 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.
 * Totem armor's effect is not regeneration. Specifically, if totem armor's effect is applied, the enchanted permanent does not become tapped and is not removed from combat as a result. Effects that say the enchanted permanent can't be regenerated (as Vendetta</c> does) won't prevent totem armor's effect from being applied.
 * Say you control a permanent enchanted with an Aura that has totem armor, and the enchanted permanent has gained a regeneration shield. The next time it would be destroyed, you choose whether to apply the regeneration effect or the totem armor effect. The other effect is unused and remains, in case the permanent would be destroyed again.
 * Say you control a permanent enchanted with an Aura that has totem armor, and that Aura has gained a regeneration shield. The next time the enchanted permanent would be destroyed, the Aura would be destroyed instead—but it regenerates, so nothing is destroyed at all. Alternately, if that Aura somehow becomes indestructible, the enchanted permanent is effectively indestructible as well.
 * If a spell or ability says that it would "destroy" a permanent enchanted with an Aura that has totem armor, that spell or ability causes the Aura to be destroyed instead. (This matters for cards such as Karmic Justice</c>.) Totem 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 totem armor, the game rules regarding lethal damage cause the Aura to be destroyed, not that spell or ability.

Trivia

 * Totem Armor was featured as rules card 5 of 5 in the Rise of the Eldrazi set.