Varsoon the Undying Quest

Varsoon of Qeynos Aquaducts and Qeynos Hills is a high level necromancer, and the target of many high-level players. In QH, he sometimes spawns in the ruins near Surefall. He is level 25. When killed:

Varsoon says, 'You have no idea what you have unleashed.'

Immediately after you kill Varsoon, Varsoon the Undying will spawn over the corpse.

Glowing Black Stone identifies as "Varsoon's Black Heart" so is there may be an interaction here. When charmed and hailed, Pyzjn responds as follows:

You say, 'Hail Pyzjn'

Pyzjn says 'Hail, Arkytz . Pyzjn is working for Master Varsoon. If Pyzjn do good work maybe Master Varsoon tell Master Bruax he is worthy. Pyzjn must go now. All glory to the Plaguebringe! May you die a painful, oozing death.