You want to know what the fucking endgame of this is? Well, in Ravenloft, there was an experiment which tried to answer this, and it gave birth to the ONLY Negative Energy Elemental EVER TO EXIST- though depowered, and offset because of an original concioussness because the Dark Powers are not stupid, and can recognize a threat, which is why they've contained gods and Elder Evils before.
That Negative Energy Elemental?
Death. Grim Reaper. Plain and fucking simple, no bullshit, had mad powers based on the expanse of it's being, would have killed everything if not for it being offset by the means of creation not fucking up and a bunch of other stuff.
Oh Right, Some dudes actually were smart enough to realize that this system basically is puppeted as fuck, slowly degrades and breeds in the means to self-replicate like a goddamed Grey Goo event, and is more or less bad for everything until one genus went
"Remove malignent will of Plane of negative Energy."
And then we got the Deathless, who are not unviable Archliches or Baelnorm just waiting to be cotnrolled by EX-Candidate for the skelepocalypse.
And then there's of course, the fact that Good, Evil, Law, Neutrality and Chaos are Defined Objective Forces with influence over unique "corruption" like aspects that are effectively like an invasive force over freewill- and Evil has MANY of these, Taint, Vile Darkness, Infernal corruption, Actual proven negative Energy exposure side effects in the Necormancers Handbook, Mortibund, Undead STDs, the works.
And a good chunk of Evil descriptor spells are under the school of necromancy, putting you at risk of this.
yeah, gee fucking wiz, I wonder why no one considers using powers affiliated with Nuclear Fallout's Meaner Eviller cousin with a prison record.
I'm not even going to go into Orcus's fucking portfolio, I've done it enough already.
So Yeah, Negative Energy Plane is sentient/makes sentiences that perform the classic Undead Spawn Cycle, and THIS IS BAD