Alonsus Chapel is the chapel, in Stratholme undead side, where Uther the Lightbringer was made the first paladin in the Silver Hand. The chapel was presumably named after Alonsus Faol, Uther's mentor and the leader of the Church of Light. The Chapel is located just inside Elders' Square from the Eastwall Gate service entrance, facing the open gate into the western districts. Despite its dingy appearance, it has survived both Prince Arthas' purge and the Scourge invasion relatively intact. The chapel is completely surrounded by zombies and skeletons, and Magistrate Barthilas also stands vigil outside — that is, until someone opens the inner gate of the service entrance.
An eternal flame has burned in this chapel at least long enough to keep the Scourge from overrunning it (and, apparently, to prevent the fires of Stratholme from consuming it) and to prevent its single occupant — the paladin Aurius — from being transformed into a death knight. In order to complete their final trial to obtain the rank of Master, Blood Knights of Silvermoon must enter into Stratholme and extinguish the eternal flame in the chapel. The chapel will go up in flames and the Blood Knight(s) and their group must defeat Aurius and the spirits of five Knights of the Silver Hand to emerge victoriously.
Although the eternal flame are supposed to keep the Scourge out, the mobs of Stratholme have no trouble following you inside the chapel.