The Immaterial Girl

The Immaterial Girl is a kill quest given by Argent. It requires killing a Boss mob.

How To Achieve
While it is simple in the sense that it is a mere kill quest, killing Mortred is a hard task since she is a high-level boss mob.

Mortred is located in dense forests, and may be found with some searching. Once her health bar is within vision, simply walk around while trying to keep the health bar on the screen. If it disappears, it means one has passed by Mortred. Note, she can be hard to see since she hides behind trees and other obstacles, but her bright blue glaive can be a dead giveaway.

Once she's located (or she locates you), try to attack her with ranged weapons and try to avoid her slowing daggers, they apply a Slowness II effect on you for 10 seconds. Try to stay as far from her as possible, since her damage is very high and unless you are a high level or have good armor, she can tear you down in a few swipes.

Do battle with her, and simply deal the killing blow to her (must be you and not another player, a mob or something else). Once so, you have completed the quest, then interact with Argent to get your reward and clear the quest of your active list.