This quest can be found in Sunstone Rock. Located off to the left of Cauldron Xi. You will find a herd of Behemoths attacking the town. Kill the Behemoths and enter Sunstone Rock through a passage to the left of the main gate.
Probably the best way to deal with the Behemoths is to destroy its large belly component and then aim to destroy the six components around its head. Those components power the Behemoths gravity controlling abilities. Destroying those will stop them from hurling rocks.
Talk to Janeva
Go inside Sunstone Rock and speak to the Warden, Janeva. Janeva will ask you to find 3 people at different locations and kill them.
Find and Kill Ullia
The nearest one to Sunstone Rock should be Ullia. She'll be in a nearby Bandit Camp. If you already cleared the Bandit Camp before the quest she will be standing around the entrance of the camp. Defeat her and continue on to the next one.
Find and Kill Gavan
Gavan's where abouts can be found at the inn marked on your map. Speak to the Innkeeper and then scan the area for clues. Follow the tracks to a bunch of smugglers and take them out and then speak to Gavan.
Find and Kill Rasgrund
Rasgrund can be found to the South West of Meridian, right next to a corrupted zone. Taking on Rasgrund will be a task as you will have to navigate to where he is and simultaneously avoid the traps he's set up for you. Make it to the top where he is and a cut-scene will start.
Report to Janeva
Speak to Janeva to report what happened to the three targets and complete the quest.
I’ve cleared sunstone rock thrice now, but Ullia is nowhere to be found. I hear her, it appears she is already injured but I can’t find her anywhere