BDv21 Gold Invulnerable revenant Thread - Brutal Doom mod for Doom

Finally caught this bitch, got reproducible behavior after loading a save: Chebmaster.com

Zandronum 3.0 (Sep 03, 2017) + KSUTRA.WAD + brutalv21.pk3 (May 18, 2019).

One revenant (was he resurrected by the 4 arch-viles just beyond the corner?) is invulnerable to anything but bfg9000 and has no monster description when aimed at.

If he grabs an imp body from the floor to lob at you, he becomes mortal again, with description showing properly.

Hmmm... Do revenants use imp bodies for throwing or are the imps being raised by the arch-viles and insta-fragged by that uber-revenant? (I mean, is he uber with him playing Heavy and arch-viles playing Medic? Can they do that?)
If he grabs the bodies, why then does he smack them around eliciting roars of pain? Were those imps merely playing possum? There is much devilry around!

Here he is again (the same megawad, different map): Chebmaster.com

Fun fact: these invulnerable revenants stop railgun beam (cause immediate explosion if it hits them).

Okay, most important detail to date: if you walk into his meelee range, he hits you once then proceeds with imp beating even if there was no imp live or dead close by. But there were some imps around. So, this invulnerability *may* be glitchy (interrupted) fatality on an imp.

Addendum: marine NPC companions ignore the invulnerable revenants.

Also, they have *total* invulnerability (my earlier observation about bfg was erroneous), which they lose if you go into their melee range, proceeding with imp beatdown.
As soon as I provoked it into beating the imp it pulled from its pocket -- that's some hammerspace mojo -- my NPC marines standing nearby opened on it annihilating in in a second.