Energy shield

Energy shield (ES) is a second health bar that sits above your life. Damage hits ES first. When ES is empty, damage goes to life.

What it covers. Every damage type, including spells, except poison. Poison damage ticks directly into life.

Recharge. If you are not hit for a few seconds, ES starts recharging, quickly, until full. Taking damage interrupts it, so ES shines when you can avoid hits for a moment: ranged builds, builds that kill fast, and builds that block or evade.

What does not refill ES. Flasks, life leech and life regeneration restore life only. The Wardbound Oath keystone changes that, at the price of the natural recharge (Keystones).

Where it comes from. Energy shield bases for helmets, body armour, legs and boots; spellbooks (some base ES); affixes; the passive tree around the Druid and Sorcerer; and certain ascendancies (The three defences, Affixes).

Pros and cons. ES is the great pool for casters, because spells and every element are covered. But ES alone does not stop a boss slam: a big hit empties it and the rest hits life.

Mana. The "damage taken from mana" share works on what remains after ES (Mana before life). Mind over Matter turns off ES entirely.

Monsters with the Shielded modifier carry the same idea: a barrier that comes back eight seconds after they last got hit (Monster modifiers).

Reading the bar. The client shows ES as a coloured bar on top of life.

Ratings. A same-tier ES set matches armour and evasion sets in strength against a same-level monster, but behaves differently (Armour and block, Evasion).