Deep Below Deireadh Prison

It’s a reasonably short ride southeast along the Pontar river to reach the outskirts of Oxenfurt. Follow the road for best results, locating and riding across Novigrad Gate (the confusingly-named eastern entrance to Oxenfurt). Yennefer is just beyond.

If you didn’t help the mages escape during Secondary Quest: Now or Never, you ride or walk past the impaled bodies lining the streets into the city. Yennefer laments the grotesque displays of sorceresses on spikes.

Next, you speak about entrances to the prison. Yennefer has found several. You can begin now, or stop and return to Zoltan for help. If this has occurred already, you tell Yennefer the dwarf is ready with the beer.

Follow Yennefer across town, until you reach the well in question. It seems you’re the only one getting wet. She hands you a device that you can activate when you find Margarita. Then take the plunge and drop down into the well.

Surface, swim northeast, and climb up into the remains of a once-spectacular elven sanctuary. Head roughly southeast, into a tiered chamber inhabited by a grave hag. She’s guarding a stone archway with a broken mechanism. That needs fixing in a moment. Then wade down the corridor to the northeast, which soon turns into a short swim. Climb up and into a tunnel second, curving around to the left. Enter a stagatite chamber where three drowners are waiting to be slain. Then search the lever mechanism on the wall, left of the arch you entered from (northeast). Remove the lever, which should come in handy in a moment.

Move through an archway to the southwest, into a partially waterlogged room. Turn left (southeast), cross a small stone bridge with a pile of bones on it, and back into the tiered chamber where the grave hag’s corpse is. Now you can access the mechanism to the south, insert the lever, and open the stone door.