
This first level is simply called Sancre Tor and here's what you'll need to do to complete the entire thing. Enter its courtyard and head on in through the door that you'll unlock with the key Jauffre gave you. When you arrive, you'll find several undead in the area, liches and skeletons (melee and ranged) outside, and a circular keep that marks the entrance to Sancre Tor. If you've done the Chorrol mages guild initiation quest, you can simply fast travel to Cloud Top not too far away from Sancre Tor, else simply head north from Chorrol or from another of your nearby pre-visited locations.

It's a fairly big dungeon with lots of wraiths, so unless you're a pure spellcaster, I'd advise getting one of your swords or other weapons enchanted to help you deal with them.

It lies in an old ruin called Sancre Tor, which is north of Chorrol and now marked on your map.

Now speak with Jauffre about the armor of Tiber Septim, and he'll reveal the location of the armor as well as give you a key to its door. After returning your first Daedric artifact to Martin, he'll tell you about the second part of his ritual which requires the blood of the divine.
