The quest begins upon entering Darklight Tower. The Dragonborn will be approached by an Imperial Mage, Illia, who has just killed a fellow witch. She says that the tower is evil and she can no longer be a part of its dark order. She asks the Dragonborn to help her travel to the top and kill the leader of the order, her mother. Accept, and she will set off up the stairs.
At a certain point the Dragonborn will reach a master level locked door. If the Dragonborn cannot pick the lock, they will need to venture alone down a side hallway into an inner chamber, where the player will be confronted by a witch and a Hagraven. The witch has the key. They need to be defeated and then the Dragonborn must return to Illia. Unlock the door and continue until reaching the top of the tower.
Upon exiting the tower onto the courtyard, Illia will tell the Dragonborn her plan to deceive her mother into thinking they are her sacrifice. The event begins when the Dragonborn sits in the chair. Illia attempts to backstab her mother, so as she fails, rise from the chair and quickly overwhelm the witch. She has powerful spells, but will focus on her daughter before she targets the Dragonborn. (The plan can be ignored and instead immediately kill her mother.)
When she is dead, Illia will thank the Dragonborn and suggest taking her mother's staff, the Staff of Hag's Wrath, as payment. Loot the staff as well as anything of value from the table. Be sure to check the chest in her tent for further reward.
- Illia can die during the quest (especially if you accidentally hit her while she is fighting). However, you can still complete the quest without her and loot the hag's staff from the body of Illia's mother.
- The tower contains numerous patches of mushrooms and potions, as well as a fair number of chests and treasure rooms. It can be best to complete the quest first and then explore the tower at leisure using a light source to find the loot, without having to fight a foe at this time.
- It's possible that after the final battle with Illia's mother, your follower will attack Illia (and kill her); a good idea is to have your follower wait at the top of the stairs leading to the top of the tower.
It is possible to enter Darklight Tower from the top entrance if you approach via top of the mountain next to it and jump over the wall. If you enter the tower this way you will only be able to venture up to the gate, on the lower half of Darklight Tower, that needs to be opened via a switch on the other side, which you can not do from this point. If you try to head back to the top half of Darklight Tower, Illia will suddenly be at your side (phasing through the gate somehow.) You can still activate the quest if you speak to her from there.
The real problem only occurs if you have already confronted and killed Illia's mother before meeting Illia and activating the quest. If you have killed her early, the quest will still activate and Illia will still follow you to the tower's top courtyard, but she'll just wait there expecting to confront her mother and the quest can not finish. If you sit down in the chair this seems to trigger her to return back to the tower bottom as if the quest had finished, but no conversation options will be available with her and the quest will still indicate you need to kill Illia's mother.