Misconception about Vitiate's power gained from Force "drain"
Ok, so in this threat, I want to talk about a huge misunderstanding regarding Vitiate's power he gains from Force draining.
Consider the following facts:
1. Vitiate needs to fuel his own power with countless deaths in order to use his enormous Force drain.
"Eight thousand Sith Lords gathered on Medriaas and agreed to partake in a ritual that would bind the Sith together as an ultimate dark side weapon.The ritual lasted ten days. Lord Vitiate orchestrated the sorcery and the planet Medriaas was consumed by the largest dark side nexus the galaxy would ever see. When the ritual ended, Lord Vitiate emerged as the only survivor. The pain, energy, and suffering of every living entity on the planet fueled his power and would prolong his life for centuries."
-The Old Republic Encyclopedia
2. Vitiate's stolen Force reserves are actually limited. And he uses them to keep in check his immorality.
"Lord Scourge reveals the Emperor's true goal for the war: to complete a Sith ritual that will grant him unlimited power and immortality by eradicating all life in the galaxy."-The Old Republic Encyclopedia
"His strategy would lay the groundwork for the Republic's destruction, but would also prime the galaxy for the Emperor's ascension to immortality."
-The Old Republic Encyclopedia"While generations of Imperial citizens died to fuel his war machine, the Emperor's obsession with immortality continued to burn inside him."
-The Old Republic Encyclopedia
Here is more information:
"When the Emperor broke my will, he looked into my mind, and I was able to see the reflection of his own evil. Invading the Republic is only the first step of his plan. He has become obsessed with power and immortality. The dark side is like a cancer inside him; it grows faster than he can feed it. He has consumed an entire world, but he still hungers. And with his hunger comes an all-consuming fear. He has lived a thousand years; he knows he could live many thousands more. He is terrified of death."-Revan, The Old Republic: Revan
"His hunger for immortality must constantly be fed."
-Lord Dramath, The Old Republic: Knights of the Eternal Throne
What is even worse is the fact that when Vitiate shares his longevity with his Hands' servants, he needs to drain their Force energies to maintain his own immorality.
"Servants of the Hand share their Master's longevity, living untouched by age for centuries under his command. In return, the Emperor draws on his servants' strength in the Force and body to feed his ever-increasing power, leaving the servants withered and frail."-(Star Wars: The Old Republic: Encyclopedia)
Remember when I said that Vitiate feeds on deaths to trigger his massive Force drain?
It is the case for Ziost.
Vitiate mind-controls weak beings and makes them kill each other so he could feed on the deaths they cause.
"Unleashed from his sanctuary on Yavin 4, the former Sith Emperor has now struck the Imperial world of Ziost. Using his immense power in the dark side of the Force, he has dominated the minds of the planet’s Imperial troops--as well as an elite cadre of militaristic Jedi--and has set them against the populace, engaging in a bloody slaughter."-(Star Wars: The Old Republic: Rise of the Emperor)
It is important to note what Force drain is and does.
Force drain is defined as a Force power where a Force user feeds on another's life-force/Force energies. Usually, darksiders feed on others if they are severely wounded to heal their wounds.
What does that mean? That means he or she used the Force reserves he or she has stolen to mend the damage he or she has suffered in a certain moment.
This Force drained power is not unlimited if the Force user utilizes their properties in whatever way he or she sees fit.