Emperors Guard Head concept - undead ex-Jedi

UNDEAD EX-JEDI idea - way too dark for Disney 
Just scribbling to loosen up yesterday after watching Rogue One again (best Star Wars movie I think) and got the feel for an idea on the Emperors Guard - 20 dead JEDI brought back to the Emperor after the special order 66 (movie 3) to be reanimated by the power of the Dark Side with all their JEDI skills enhanced even more by the Emperor.
Half bone, half machine encased in black Obsidian armor they are the darkest side of the Imperial Force.
Combat
They can only be killed by a Jedi's light-saber but are as skilled as a 'Darth'. What makes them even more difficult to fight is their effect on everyone but the Emperor in close contact.
When you are within 'light saber' fighting distance you begin to be converted to the Dark Side if you are a Jedi, reducing your good side as the process continues and reducing your willingness to fight the creature.

Everyone else is just rotted/ disintegrated from the outside-in within minutes, even other Imperial troops. 

The Emperor had twenty of these creatures as his personal body guard but they defected across to Snoke after the death of the Emperor. The Emperor did not bring them with him to the rebuilt Death Star (movie 6 )on Vaders request, as even he could not beat all twenty in combat and did not trust their underlying allegiance.