The Chosen One

The Chosen One is one of 's Battle Skills in Xenoblade Chronicles 2.

The specific list of effects is as follows:
 * takes all and does not lose it while Pneuma is active.
 * If Rex receives damage which would reduce him to 0, he instead is reduced to 1 HP and has invincibility for 5 seconds. (This only works once per activation of Pneuma.)
 * Rex has complete immunity to reactions and s.
 * Rex's s and Driver Arts automatically deal damage of the element corresponding to the enemy's elemental weakness.
 * Damage dealt by Rex/Pneuma ignores the damage reduction from elemental orbs.
 * If Pneuma blocks an attack, the damage is reflected back upon the attacker.
 * When Rex takes damage, the attacking enemy receives damage.
 * Pneuma strikes all elemental orbs during a, for one hit of damage each.

Overview
This skill is a major part of what makes Pneuma so difficult to kill. Rex taking all aggro is no threat thanks to Pneuma's massive 60/60 physical/ether defenses and Pneuma's passive Foresight effect, reaction/debuff immunity is greatly useful for survivability, and if all else fails the 1-HP effect is a get-out-of-jail-free card. This makes Rex tanky enough that Pneuma-focused setups need not rely on major sources of healing; this is useful if the only healing Blades are also on Rex, and may free up one of Rex's accessory slots from a crit healing accessory to one more focused on damage. Together with the fact that the other party members will only be able to be hit by AOE moves, this skill turns Rex into the most effective tank in the game.

Not all of the effects are quite as useful as the tanking-focused ones. The reflection damage and spike damage are more-or-less negligible. The damage-increasing effects are very useful in lategame, when Pneuma's damage is relatively great, but their effectiveness falls off in postgame as Pneuma's damage starts being outclassed by other Blades and her effective role accordingly switches to being more support-focused. Damaging all elemental orbs can be handy for making Full Bursts much easier (the effect makes Full Bursts consistently possible with four elemental orbs and guaranteed with five), but can be a hindrance if one wants a chain attack with many orbs to go for as many rounds as possible. Nevertheless, any detrimental side-effects of this skill are far outclassed by the benefits.