Jezebel
DLC
If you succeed his first step, it'll trigger the cultists event. She'll kill Balaam at the end of the game if you haven't the sigil, preventing your death.
Harem
Diana and Jezebel Harem, DLC Princess Harem, All Princess Harem.
Story guide
Step 1:
First you have to see Jezebel at the cave before the 11th, if you don't, you will not be able to continue the story with Jezebel.
You need at least 9 in knowledge to succeed.
Be careful because you can't trigger it indefinetely.
Step 2:
You need at least 11 in knowledge and prowess to trigger the event.
Go to the cave in the afternoon.
Step 3:
Go to the library in the afternoon to acquire the Necronomicon.
Step 4:
You need at least 13 in prowess and knowledge to trigger the event.
Go to the cave.
If you have less than 15 in prowess, you'll achieve a new sex scene and die.
If you have at least 15 in prowess, you won't unlock the sex scene, but you can proceed to step 5.
Step 5:
You need at least 17 in prowess and knowledge. It trigger at night - it can trigger right after the step 4 if you meet the requierements.
Step 6:
You need at least 21 in prowess and knowledge to trigger the event, and at least 24 in prowess and knowledge to succeed it.
Go to the cave.
If you accept the deal, you'll continue the Jezebel path.
If you refuse the deal, you won't continue the Jezebel path, but it's the only way to achieve the full seven harem.
Step 7:
You need at least 25 in prowess and knowledge to trigger the event at night.
Accept the offer. If you refuse, well. I'll let you guess.
Step 8:
You need at least 30 in prowess and knowledge to trigger the event and to have at least unlocked the fifth step of Charlotte, Diane or Blanche. It can be the fourth step or the sixth step for one of them, not so sure about this one.
Go to the cave and offer a princess. The one you choose will disappear from the game.
(You can now marry Jezebel)