Yalsis, the Igniter

Yalsis, the Igniter was an Ultra Fallen Vandal encountered at the Watcher's Grave on Nessus when it was featured as the weekly Flashpoint.

Gameplay
Yalsis will appear at the Watcher's Grave when an the Ether Resupply Public Event is active, during a Flashpoint. If you are able to bring down the boss's health down to sixty-six percent within the first minute, a message will pop up in the corner of your screen, reading "The Servitor calls for reinforcements." As soon as you receive it, a Skiff will warp in at the far side of the battlefield, and the Igniter will arrive.

Yalsis uses a Molten Welder as their weapon of choice, capable of rapidly firing volleys of Solar projectiles that travel long distances. Being a Vandal, they are incredibly agile and will quickly strafe around to dodge incoming fire, and can also scurry around the area to change position. They will sometimes begin charging towards the player to slash at them with their claws. Yalsis will despawn shortly after the Public Event ends, so it is imperative to take them out as quickly as possible. If you manage to defeat the Ultra before they leave, they are guaranteed to drop three Nessus Tokens and one Rare Engram, but it is possible for it to grant up to two Legendary Engrams.

Trivia

 * The Igniter shares their name with Yalsis, Devil Claw, a House of Devils Vandal who randomly appeared in the Fallen S.A.B.E.R. Strike in Destiny.

List of appearances

 * Destiny 2