Ulder Ravengard
Ulder Ravengard was the ruler of Baldur's Gate. At the suggestion of Thalamra Vanthampur, he had met with Thavius Kreeg to discuss improving relations between Baldur's Gate and Elturel. Was inside the city when it disappeared.
Ulder was later found to be in control of a small portion of the western side of the city in Avernus, along with what remains of the city's civilian and religious government -- Wöbaer Triest (Acting Secretary of the treasury), Lor Ryken (the ambassador to Iriaebor and self-appointed logistics officer), Hilde Kaas (the highest-ranking surviving Hellrider), and Pherria Jynks (the highest-ranking remaining priest of Torm) -- and a mixed force of Hellriders, Companions, and Flaming Fist.
In return for making contact with Ikaia and his people -- and building a bridge over the gap in the Maze to literally link the two groups -- he asked the party to retrieve a holy relic of Helm from the Grand Cemetery.
