This monster by Ed Greenwood shows up again in a book called Mythic Races as open content with some changes.
It's interesting, because they are very much a race of Mary/Marty Sues.
Mostly immune to magic, having whatever class levels the DM wishes, 85% magic resistance, immune to mental attacks, fire, cold, and life drain, and effectively immune to death.
You see, they are cursed.
Yes, there is a stipulation that they will act despondently and strangely 1 in 20 rounds. But mostly they are immortal killing machines. Sometimes immortal killing machines infested with rot grubs.
That said, the idea of a deathless opponent, one who you can communicate with, one that you cannot destroy has interest. Especially since they can be created from extant creatures in your campaign with a bestow curse and a wish.
Hack & Slash