I had too much weight so went to the bank in Sanctus Seru, and met this guy along the way, near to the bank I would think, as he ran up to me as I cliked the banker. So no where near Seru's spawn site. Right after this guy died, there were two of them on track, one likely a spawn from a few days previous and one probably from the time the zone came up. This one must have seen invis to aggro on me, which is very uncommon outside of the guild halls in Sanctus Seru, and he was 'immune to changes in its run speed'. He didn't run at the end of the fight, which was right next to the indifferent banker. Easy fight for a 75 ranger and a bunch of aa's and epic 2.0, and as a single mob. Maybe not so easy for someone not so fortuanate, who happened to get adds. Max hit was a double for 146 and 140. Most of the time he missed. Loot was a combine spear.
I suspect this guy may be a zone wide roamer. But that is pure speculation.
I just happened to have a spy zone into check on the status of Lord Inquisitor Seru, and this guy walked along the far two walls from where my spy was camped. My spy was camped in the corner of Seru's room which is closest to the zone in spot from the maze on the floor below, but not in that hallway. I believe i saw this happen once before but don't know the mobs name from that episode. I don't think I have ever previously seen this mob on the floor with Seru's room. Besides Seru, all the other mobs on this floor are of the 'a praetorian xyz' flavor. Maybe this guy was lost, or a wanderer who makes a once a day pass through the room, or something like that. I comment on this because I have camped Seru for many hours, and only seen it once for sure, and maybe twice.