Halren

The white-haired, robed dungeon-lord at the heart of The Snatcher's Cave's burial chamber, and — per the gravekeeper's diary — one of the four ancient immortal scholars of the Hollow House, a research-tomb where they studied a pair of Elder-race tablets that granted them unnaturally long life. A high-level spellcaster, slain by the party in Session 42. His name is badly garbled in the recording (Halren / Halren / Halren / Halren and more).

Session 42

• The boss of the chamber. Climbed out of the central sarcophagus when the party opened the sealed doors — knee-length white hair, hood, robes, a staff in both hands, an aura of dread. As a free action he bubbled the absent Lash out of the fight.
• A spellcaster's arsenal. Chain lightning, a twin-cast 6th-level lesser Feeblemind that dropped Silithane and Pimothy to 7 INT, a 4th-level Slow (repeatedly reflected by spellbreaker Fenric), Shield, Blink, and a final Fireball that downed Pimothy and nearly killed Magra. Killed by Fenric's finishing blow.
• Loot. A key was hidden inside his ribcage, opening the back treasure vault; he carried a minor-magic spellcasting-focus staff (kept by Silithane) and a trace-magic robe.
• The Hollow House lore. The gravekeeper's diary names four scholars who studied the Elder tablets and gained long life: Corvian (died first), Bael'Drakkor (sharing the name of the Baelheim tribute-warlord), Halren himself (also "Halren"), and Jairus — the last survivor, who spoke the ancient words and may still be alive today. A black-haired unaging woman, Laila, is also named (died second). The house's name drifted from plain "Hall House" to the dreaded "Hollow House."
• The other scholars' tombs. Two flanking statue-sarcophagi in the boss room (an elderly man with a hammer; a younger man with a two-handed axe) and two noise-activated lower tombs likely hold the other scholars (Bael'Drakkor, Corvian) — left undisturbed rather than risk two more Halren-like mini-bosses. A fresh immortality thread.