Adrenaline

Adrenaline is a resource that some Warrior, Paragon, Dervish and a few PvE skills require as a cost instead of energy. It is represented with the icon in skill listings.

Gaining adrenaline
You gain one "strike" of adrenaline every time you hit an opponent with a weapon (attack skills which attack multiple opponents will grant one strike for each opponent). You also gain a small amount of adrenaline whenever you take damage. Some skills, such as "To the Limit!", can be used to gain adrenaline as well. Other skills can affect the rate at which you gain adrenaline, such as Infuriating Heat and Soothing. Each adrenal skill has a separate pool of adrenaline; adrenaline is not divided between pools. Ergo, bringing multiple adrenal skills will not decrease the rate at which individual adrenal skills charge. Adrenal skills cannot hold extra adrenaline.

Testing indicates that adrenaline is actually measured in units smaller than strikes. Each successful attack provides 25 units of adrenaline, and each "strike" in a skill cost represents between 20 and 25 units of adrenaline, varying between skills. In comparison, losing 1% of your health due to damage (not degeneration) will provide one unit of adrenaline.

Adrenaline gain multipliers are capped at +100%. Focused Anger is the only skill that can theoretically bypass the 100% cap with enough attribute points; however, due to a long standing bug, it does not have any effect past 100% additional adrenaline gain. This cap does not affect skills which give strikes of adrenaline on hit, like Dark Fury and Infuriating Heat.

Spending and losing adrenaline
When your adrenaline is empty, adrenal skills will have dark icons in the skill bar. As you gain adrenaline, these icons become brighter and flames creep up them. When the flame effect vanishes and the skills are fully bright, they can be used. (Note: Some unofficial user mods will alter how adrenaline levels appear.) When you activate an adrenal skill, the adrenaline charged up for that skill is reset to zero. All of your other skills lose one strike (25 units) of adrenaline. This adrenaline loss will be incurred even if the activated skill is interrupted or fails; however, if the skill was an attack skill and that attack hits, that hit will in most cases reclaim the lost adrenaline. Some attack skills, like Dragon Slash will even regain extra adrenaline if they hit.

All of your adrenaline will naturally be lost after 25 seconds of not attacking, not sustaining damage, or otherwise gaining adrenaline (such as by using Rage of the Ntouka). You will be warned if you have partially filled adrenal skills as they will begin blinking. Some skills such as Wild Blow and Sympathetic Visage also cause adrenaline loss. Disabled skills also lose all their adrenaline, and disabled and recharging skills cannot gain adrenaline.

Pre-building adrenaline
In PvP, adrenaline users will typically carry a spear in one of their weapon sets (and frequently carry a bow in their inventory, as well). Even though attacking with the spear does little damage, it gives the user a chance to build adrenaline at range before closing in or while snared. Spears are used because it has the fastest attack speed of any ranged weapon which translates to faster adrenaline gain, and because they can also have increased adrenaline gain weapon modifiers. Historically, before spears were available, wands were used instead as that allowed the warrior to still carry a shield.