Silver Sword: Walled Up Alive In Est Tayiar

Search the northeastern part of Novigrad, and the Gustfields Territory in particular, to uncover the elven ruins of Est Tayiar. This ancient subterranean labyrinth is also said to be the hideout for Phillipa Eilhart. Visit the overgrown ruins, ignoring (or battling) any witch hunters on the surface. Descend down the slit of earth at the entrance.

Use Aard to break a loose wall to the southeast, when you’re down below in an entrance chamber of elven tile floor. The wall reveals a small antechamber with a corpse to loot. Read the notes the professor left; it references Castle Drahim. The Witcher apparently murdered one of the professor’s men and left the poor fellow to die in here.