I found these musings of Plagueis interesting:
If one accepted the tales handed down in accounts and holocrons,
the ancient Sith had known how to accomplish this. But had Sith like Naga Sadow and Exar Kun genuinely been more powerful, or had they benefited from the fact that the dark side had been more prominent in those bygone eras? Some commentators claimed that the ability to survive death had been limited to those with a talent for sorcery and alchemy, and that the use of such practices actually predated the arrival of the Dark Jedi exiles on Korriban. But sorcery had been employed less to extend life than to create illusions, fashion beasts, and resurrect the dead. Powerful adepts were said to have been able to saturate the atmosphere of planets with dark side energy, compel stars to explode, or induce paralysis in crowds, as Exar Kun apparently did to select members of the Republic Senate._