I say Nihilus.
"Nihilus consumed entire planets on several occasions, caring only to appease his hunger. The dark side consumed him more and more each time, causing his hunger and power to grow dramatically."
"Knowing that he would succumb to death if he did not act soon, Nihilus ripped his spirit from his body and encased it in the armor he wore, thus allowing the dark side to consume his useless body. Using the Force, the Sith Lord was able to keep his robes, armor and mask together, giving him some form and allowing him to use his Force powers as well as a lightsaber. Apart from that, however, he no longer had a physical form and became simple, primitive intent."
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