Gorso the Nightmare King is a Darkside Worldboss found on Alderaan. He is part of Galactic Season 10 DvL Event and previously Season 7 and 8.

Gorso the Nightmare King

Gorso the Nightmare King spawns on Alderaan in the Glarius Valley. South-East of Outpost Ghrent for Imperial Players nearby a snowy tree and rocks.
X -415 Y 200

Strategy

Gorso the Nightmare King has two mechanics that need to be avoided, he alternates using both of them although they can happen at the same time.

Every minute or so Gorso the Nightmare King will apply a poison DOT to your character, you either need to cleanse it yourself, have a healer cleanse you or use a medpac to survive it.
Tank players should take priority when being cleansed, if you are a DPS player and the boss has a high amount of HP it may be easier to die, respawn and run back to the boss.

All players both melee and ranged need to be careful for the White Lightning AOE circles. Every 30 seconds light white circles will spawn under random players, you will only have 5 seconds to move before bright purple lightning activates in the circle, making part of the floor around the boss deal damage if you stand on it.
This can be hard to see on Hoth due to blending into the snow.