Ultimate Sacrifice

Ultimate Sacrifice turns your Aura into a berserk state with a bill attached. Popping Aura breaks your current limits: output increases to 125%, the Aura becomes uncancellable ("Your rage is born from deep within your heart. Nothing can stop it"), your aura animation changes to a modified version of the Last Stand emote, and a black-and-white cosmetic VFX surrounds you for the duration.

Then the curtain falls. When your Aura ends, you lose 50% of your maximum health and your output is reduced to 75% for a period of time. Documentation notes one mercy: the health loss cannot execute you - it will only lower you to 1 HP at minimum. On top of the crash, you build aura more slowly overall, so the windows come less often. As the tooltip puts it: "The ultimate sacrifice... has the ultimate price."

The charm rewards players who can guarantee a kill inside the empowered window and survive - or disengage through - the vulnerable aftermath. Note that uncancellable is also a drawback: you cannot end the Aura early to dodge the timing of the crash. It requires Level 15, weighs 1 wt., and is documented as found in Hueco Mundo.