undertrap(gaster)(you can make au versions of him if you want)

Description: gaster is the leading royal scianest and the main bad guy in undertrap,he is the most powerful monster in the underground apart from papyrus and king asgore,he was the one who masterminded the death of chara and asiral and he tricked them into thinking they could restore peace between humans and monsters,he then drained some of charas deterimation and injected himself in the eye with it causing glowing red cracks in his eye and giving power at the cost of his soul becoming incressingly corrupted by the DT,he injected the same DT into sans and papyrus,and when they ran away,he was angry,not only that,he was angry over the fact alphys was becoming in control of everything,so he hatched a plan to make it look like a disaster gone wrong,while alphys was looking at her creation,the DT extrater,gaster walked inside and prepred to push alphys into the core,but sans was inside as well and step in his way to stop him,and the next thing gaster knew,he was now back in his lab and nobody he talked with knew about alphys,maybe his plan worked,then he found himself at papyruses bedside with a bad wound and his soul nearly shattered,gastersaw his chance and injected the same DT as sans and gaster,he then began to use papyruses soul to invert his traits and turn him into a murderus sociopath,he now waits for the final human soul so he can take the 7 human souls and destroy both humanity,the barrio,and anyone who does not agree with his plan for his world order on the surface,he has gaster blasters that are bigger then 3 papyruses,and has purple and red bones,and can use DT at the cost of his soul starting to melt more and more,on the netrual route,after you fight him in the true lab and after you kill papyrus and asgore,if you took gasters phone seen in the true lab,he will call you,thanking you for killing the only people who could stand a chance against him,and now he will rule the underground,killing all the weak monsters and subjecting the strong to tests of DT so they will be his loyal servents and he made monster kid a pair of robotic arms and he made snowdrake a royal guard,and he now rules as king,awaiting the last human soul,in the pafiest route,he is takes the human souls and nearly becomes a god,but the power of the human souls rebel against him,causing him to be dragged in the void towards his final but unknown fate,and in the genocide route,he escapes the humans rampage,but papyrus,now a amalgamate from all that DT absorbs him and finishes him off ending any chance of the underground having a powerful leader