Overcast

Effect
Exhaustion reduces the character's maximum energy. When Exhaustion occurs, the caster loses 10 maximum energy. The amount of maximum energy lost is shown at the right end of the energy bar (Default) as greyed out. Maximum energy is recovered at a rate of 1 point of energy every 3 seconds.

Exhaustion stacks. A character repeatedly casting exhaustion spells will repeatedly reduce their maximum energy, lower and lower each time. Exhaustion can lower maximum energy below zero. In this case, the deficit is regained at 1 point per 3 seconds before regaining positive maximum energy.

Source
Self Exhaustion:

Some Elementalist skills exhaust the caster. Exhaustion triggers at the start of casting (like adrenaline or energy costs), not upon resolution, so the caster is exhausted even if the spell is cancelled or interrupted.

The following Elementalist skills cause exhaustion:
 * Energy Storage: Energy Boon, Ether Prodigy
 * Air Magic: Chain Lightning, Gale, Lightning Surge, Mind Shock, Ride the Lightning, Shock
 * Earth Magic: Dragon's Stomp, Earthquake, Obsidian Flame
 * Fire Magic: Meteor, Meteor Shower, Mind Burn, Double Dragon
 * Water Magic: Maelstrom, Mind Freeze
 * No Attribute: Second Wind

Other Sources:
 * Equinox (causes all creatures to suffer double exhaustion if exhausted)
 * Arcane Languor (whenever target casts a spell while hexed)
 * Exhausting Assault (if successful at interrupting a spell)
 * [[image:Monster skill.jpg|15px]] Crystal Haze (whenever target uses any skill that costs energy while hexed)
 * The Environmental effect, Sheer Exhaustion, causes exhaustion on any spell cast under its effect.

Removal
Exhaustion naturally recovers one maximum energy every three seconds. Death removes exhaustion, but there is currently a bug that prevents the Energy bar from properly updating after being resurrected to indicate that all Exhaustion is gone. Changing zones also eliminates all exhaustion.

Prevention

 * Glyph of Energy (prevents your next spell cast from causing exhaustion)