Labyrynthia still had knowledge to share? That was a notion that the peers among the Mage's Guild thought impossible. When the Dragonborn assisted them in their plight and saved them from endless stagnation, they sealed the ruins once again and were content to leave it be, imagine their surprise when the other factions of Skyrim dropped in for a hello, and with no Dovahkiin to lead them, they've elected a new leader; Josiah Vanheldt.
Josiah elects to take the fight to them and guard the ruin until they can find the mage they enlisted to help seal the entrance from intruders.