Background:

Xoleras' real name is Dimitris Theofilopoulos. He lives in the Tucson / Phoenix area of Arizona, and is what you would call old-school. The earliest recording in which I have seen Xoleras is dated May 25, 1995, and he appeared to be near or at his peak skill-wise in the recording.
 

Stylistic information:

There was a group of early-ish players who worked hard on perfecting their Doom2 Map11 game, the group included NoSkill, Xoleras, and no doubt some others. Xoleras' local dooming partner, whom he played on Map11 a lot, was named Hijinks. I wasn't around at the time so I can't say a lot about the group, except that most of the group quit playing Doom2 before I got involved. Which player was "better" than which is beyond me. When I came onto the scene, Xoleras was the only remaining active player with this kind of highly developed Map11 game, and I  played him twice modem to modem there.

The first time I played him on Map11 was, I believe, sometime around the summer of 1996, and he was near or at his peak. Here's what it was like. It felt like he owned and controlled the map, and I was just in there to be killed in exactly the way, and in exactly the locations, that he decided. He would come out of nowhere and either kill me or force me to kill myself, and it was all so purely and obviously deliberate. There was no real fighting between us, it was just me trying to come up with something, any strategy, any weapon, any idea, that could possibly get me at least one frag. Absolutely nothing worked, and we ended the game at 75 him, -7 me. Most of the self-kills had happened directly in front of Xoleras, and he had ammo and could have killed me easily, but he had decided not to kill me with the weapon in those instances.

It remains one of the most amazing games I have ever played. I've gotton whacked on Map11 by other players, but none had this degree of complete control as Xoleras did.

Xol was good on other maps too, and he definately had a strong Doom2 Map1 game. I have no idea how he would have done on Map1 against the modern Map1 specialists, although he tells me that he came out of retirement shortly before DMcon2 to play Sslasher modem to modem on Map1 and won that game. Sslasher would have been at or close to his prime at that time.
 

Other details:

I've never seen Xoleras in person (saw two pictures tho). People who have seen him in person describe him as being 6'2" to 6'4", medium build, dark hair, having lots of tattoos, and an intimidating aura. At one point he had long hair, but it might be short now.