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 was badly garbled in the recording (heard as Halryn / Alren / Halbrand / Howren and more); Halren is now confirmed by the gravekeeper's own document, which titles him Master Halren of the Hall House.

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. (Per the gravekeeper's own document the other three are Corvene, Vaela and Jerris — and Jerris was never buried at all. See The Hollow House.)

Master Halren, in the gravekeeper's own record

The gravekeeper's diary "The Loge of ye Gravekeeper" — the document Silithane translated at the table in Session 42 — gives Halren a life before the sarcophagus, spread across generations of a single parish gravekeeper's working career.

• The eight-year argument. Carrying coal into the Hall House, the gravekeeper found Halren and Vaela "near came to blows" over a stone-slab after eight years of study: Halren swore the mark meant sunlight, Vaela danger, and old Jerris muttered it might mean both at the same time.
• The breakthrough he tried to hide. Years later the gravekeeper walked in on the scholars in rare excitement and caught Halren hiding a slab of wet stone poured into a mould of an indent of a history — markings deeper than any seen before, "arranged in lines and boxes and patterns." Halren said they had made a breakthrough and hurried him out. (Plausibly one of the work-tablets or the deciphering tablet itself, though the record does not say so.)
• His answer about the aging. Pressed on why the scholars lingered "as if time walketh slower in their hall" while the gravekeeper's own hands stiffened in winter, Halren said only that "the study of the Ancients teaches patience above all things." The town drew its own conclusion: "some physic in the old stones, some draught or powder what keeps death from the threshold."
• How long he lasted. "He was old when I was young. Old before my father died. Yet he lingered as if death forgot him." At the end, he outlived his sons, and one grandson besides — and was buried in the east row on the 2nd Day of Water, Year of the Praised Reache, third of the four to go.

Same man, or GM name-reuse?

Same man, high confidence. The record is not a second document about a coincidentally-named scholar — it is the diary the party pulled out of this crypt's treasure vault, alongside the gravekeeper's own tools and ring, and its Halren is a Hollow House scholar who visibly did not age, exactly as the Session 42 translation reported. The dungeon-lord climbed out of the central sarcophagus of that same hall's burial chamber with knee-length white hair "grown over an impossibly long life." The record simply supplies the funeral the party's boss fight undid.

The one loose end worth keeping visible: the diary buries him "in the east row," which reads like a row of graves rather than the crypt's central sarcophagus. Either the gravekeeper's east row is a row of the Hollow House's own tomb-hall, or Halren was moved — or moved himself — into the centre at some point after burial. Unresolved, and flagged for the shared Discrepancies doc rather than smoothed over.