Some Xerxe and Ger lore :D
Xerxe is dead and is in force limbo, so he can interact with the living world and some of the dead world/force afterlife (but not completely on either end) Ger on the other hand, his soul is split between the living world, part of the force afterlife, and this pocket dimension only Shrikes can enter. Xerxe's Force contract binds the entire soul, but Xerxe can't reach the part of Ger's soul in the pocket dimension, so the contract doesn't hold.
Xerxe perceives this dimension while Ger is held on Bora Vio, and he tells Suu Tei to experiment on him to try and find a way to fully control Ger, thus all the horrible experiments. None work, and Xerxe resolves to do it the hard way. Ger's spirit and hope breaks when he calls out to Mace Windu when he passes outside orbit and the Jedi runs off, startled by Ger's force signature.
Xerxe takes advantage and slips (more like smashes) into Ger's mind and torments him by tearing his memories apart, he has to do this CONSTANTLY as Ger is is subconsciously trying to fix himself. Caesar's death snaps Xerxe's control, but the damage is done and after Caesar dies, Ger is kind of reduced to a mental state that is less than Smeagle. The Blackouts then try something and meditate for hours with Ger over the course of months to restore his mind, and Ger is still doing that on his own to hold himself together. The force is literally the only thing keeping him fully sane, so when Matten (bitch) cuts him with a cursed cortosis blade, and Ger's force ability is reduced (not fully cut) Ger becomes more erratic, forgetful, paranoid, fearful and aggressive.
Another fun tidbit of Lore that gives Ger and Xerxe eerie similarities is the fact they have the same line, "I want it to be quiet", but they want quiet in different ways for different reasons.
Xerxe is caught in a limbo, not allowed the serene peace of afterlife and not allowed the relief of true physical shape and form. It drives him mad. So he he strives to tear the force apart, leaving no life and no afterlife, "I understand that when I succeed I will not no longer exist as well… that is okay."
Ger on the other hand is tired of fighting, but upon having the force he sees and feels the full extent of life and wants to preserve it, but he wants the killing and war to end.