History of Brilliant Instability

Brilliant Instability is a King's Fall raid triumph: use unstable Light to defeat Golgoroth.

How to complete

1. In the Golgoroth encounter, one player in the damage team gets the Unstable Light debuff (screen turns sickly green; timer in the lower left).
2. When the timer ends the carrier explodes and kills anyone too close, so the carrier must move away from the group.
3. The triumph requires killing Golgoroth with the unstable Light mechanic; sources I opened describe the mechanic only, not the exact objective trigger, so the precise condition (e.g. damage dealt by the explosion) is unconfirmed.

A patch fixed a bug that gave two players the debuff at once, so it may behave differently from older reports.