Well here is something for everyone's personal enjoyment... I don't know if it true or false... I just found this on the internet, so enjoy...
Origins
Darth Nihilus suffers from constant pain when his parents are of two different races: - an insectiod race and near human race. That he has major physical defects that his body sometimes rejects him by having his nervous system, his immune system and his respiratory system. Firstly, is his respiratory system, which his heart almost shuts down that his heart needs more power to sustain it and his lungs sometimes find it hard to breathe. Secondly, his nervous system is out of sync like when he feels different to temperature change. Thirdly, is his immune system which his immune system does sometimes attacks his own cells than fighting foreign organisms. Also, he has other defects like his face is mess up that it looked like his face messed up so that it looked like a complete mess. This is why he wears isolation mask and cloak but rarely can he take his whole suit off. Also, his very speech can inflict pain and death to people who are near him.
Background Info
Little is known of Nihilus's true beginnings, other than the fact that he was a survivor of the Mandalorian Wars, and may or may not have at one point been a prisoner of the Mandalorians. After the war he was found by Darth Traya to be Force-sensitive, and she began training him in the ways of the Sith at the Trayus Academy on Malachor V. After his true powers and potential were realized, Nihilus, along with fellow Sith student Darth Sion, plotted and turned against their dark mistress Traya. They cast Traya down, stripped her of her power, and expelled her from the Sith Order. Nihilus and Sion had now begun their shadow war against the remnants of the Jedi Order. They hunted Jedi to the brink of extinction.
Darth Nihilus ravaged and consumed whole worlds, to feed his insatiable appetite for power, from the bridge of his flagship, the Ravager. Nihilus powers were so all-consuming that all those who came into contact with the Sith Lord became slaves, mindless servants to his will. Darth Nihilius was once the greatest Sith Lord.
One such servant of Nihilus was Visas Marr, a Miraluka female from Katarr, a planet consumed and destroyed by Nihilus. The Sith Lord sent Visas on a mission to find and bring the last of the Jedi before him, so that he could consume his power and essence. However, this would be the mighty Sith Lord's undoing, for the Jedi exile broke her from Nihilus's bonds, and she turned against her former master. Along with the exile and Mandalore, she defeated him on board the bridge of the Ravager. After his death, his body dissolved in an aura of dark side energies.
What happened to Nihilus after his body dissolved is unknown. Whether he is truly gone, or should return again to challenge the Jedi and the Republic, shall remain a mystery. Interestingly, his true identity is not revealed even when Visas looks at his face after his defeat, leaving questions about whether his previous personality may have been anyone of consequence.
But before Nihilus was supposedly killed, his essence traveled to one of the Leviathan Class Destroyer and they all left the battle over Telos when first true Star Destroyer, Ravager was destroyed and whereabouts of this destroyer and others is unknown. Only he knows where it is. He has two HK-Series Droids that these droids are assassin and protocol droids and serve as pilots. The reborn Nihilus went into stasis for a very long time that his droids were always kept an update of recent events. Now he is eager to regain his lost title as the Sith Lord.
Darth Nihilus no longer consumes the Force from Force-sensitives in order to stay alive now since his hunger is gone. He no longer has his voice to cause any pain and death to those who hear it. For thousands of years, his connection to the Force is weaken since he was under ice for a long time.