(1) When you enter the crypt's first chamber, corpses and skeletons will attack. Corpses rise from the floor, and enemies emerge from the upright coffins throughout the crypt. The extra surprise attackers can easily flank you and disturb your battle plan if you don't act accordingly.
(2) A desiccated shambling corpse and its skeletal buddies make your life difficult in the second chamber. Don't charge into the room and get surrounded; stick back near the entrance and fight from cover.
After the fight, proceed south if you want to leave the crypt quickly. If you want to pursue the "A Maiden in Distress" side quest, follow the Lonely Soul to the east.
(3) The "maiden in distress" reveals herself as a hunger demon. The demon has been looking for a stronger body to inhabit, and you fit the bill. The fight is on unless you have a high Coercion score and can talk the demon out of a conflict. Putrid devouring corpses join the battle a few seconds in. Lock your tank warrior on the hunger demon while the rest of the party kills off the corpses.
When you have no corpses to hack, concentrate all your efforts on the hunger demon. After the hunger demon falls, the Lonely Soul will thank you for freeing her true soul. Don't forget to grab the essence of magic in the back corner before you leave.
(4) Pick up an essence of cunning in the corridor leading to the final chamber. Clear out the skeletons in the chamber to reach the exit to the Baroness's Manor.