1. Wait one day
Lacra needs a little bit of time before we talk over her idea in detail. I should hold off seeing her until tomorrow night.
You need to wait a day before Lacra is ready to continue this quest.
2. Talk to Lacra
I should talk to Lacra whenever I'm ready to discuss her idea with her.
Return to the tower and talk to Lacra. Pick "You had some idea to talk through?" and she'll talk to you about Mihai and Kallias.

The you'll automatically travel to a new location in the Silts.

3. Uncover Kallias's secrets (6 Time Segments)
Lacra believes that an ancient vrakhir who used to live in Vale Sangora in the days of St. Mihai might have known something about the ritual Brencis wants to conduct. If we find his lair, we could get our hands on his research.
3.1. Reach the roadside shrine
There is an old shrine to St. Mihai in the swamps. It will serve as a good starting point for our search.
Make your way through the swamp until you reach the roadside shrine. How you handle the conversation with Lacra does not matter much. At most, it will take a little more time, but the wisps will appear there eventually.

3.2. Follow the wisps
Will-o-the-wisps, attracted by our pain, have appeared around the swamp to guide us to our treasure. We should follow them... but carefully.
Follow the wisps, and they'll eventually lead you to a stone circle with a tomb at its center.

3.2.1. Investigate the stone slab
The wisps led us to some kind of old stone slab. Does it have anything to do with Kallias?
Examine the tomb and then have another conversation with Lacra to trigger the wisps to appear again.

3.2.2. Defeat the enemies
The wisps led us into ambush. It won't kill us, but it sure is annoying.
Follow the wisps forward. After a moment, a few zombies will appear that you will need to defeat.

3.2.3. Defeat the enemies
Again, ambush! The little pests are having too much fun with this seeing how we're already cooperating with them.
Following the wisps further, they will lead you to another location where another group of zombies will attack you.

3.2.4. Defeat the lizards
Those tricky bastards led us into a trap! Now we need to deal with hungry bog lizards.
Moving further, you will fall into another ambush, this time attacked by large lizards.

3.2.5. Investigate the area
The wisps led us to a surreal clearing in the bog, changed by some corruptive force. We should see what has happened here.
Following the wisps further, you will eventually reach a demonic-looking clearing. All you need to do is inspect the vine in the middle of the clearing to find a severed arm.

Thoroughly examine the severed arm. You will conclude that it is the arm of St. Tobias.

3.2.6. Defeat the hellhounds
Another ambush! The wisps are toying with us. We need to get rid of the dogs.
As soon as you examine the arm, hellhounds will appear, which of course you have to deal with.

Have another conversation with Lacra to summon the wisps. Once they appear, they will lead you near a rockslide.
3.2.7. Investigate the rockslide
The wisps led us to a suspicious rockslide. Something is off - we need to take a closer look.
Take a closer look at the rockslide, and Lacra will use her abilities to clear it and open the entrance to the cave.

3.3. Explore the sunken crypt
The wisps have now led us to an old crypt sunken in the bog. Could it be Kallias's lair? We need to investigate the place.
In the first room, there are a few things to examine - a painting on the wall, notes on the shelves, and items on the table - but you do not need to do this. You can move on right away.

Once you pass through the green door, you will find yourself in a room with frozen zombies. When you try to leave this room, they will come to life and attack you.

3.3.1. Defeat the undead
The crypt turned out to be swarming with the undead, kept animated by Kallias's corruption. We need to dispose of them.

Moving further, you should pass by the frozen corpse holding a book. Take the legendary greatsword stuck in it - The Vrakhir.

Using shadowstep, get past the gap in the floor, and after a moment you will reach a chamber with a large sarcophagus in the middle.

3.4. Inspect the sarcophagus
We found what appears to be Kallias's resting place. We need to look inside the sarcophagus.
Check what is inside the sarcophagus. It turns out to be empty, and a few enemies will spawn in the room.

3.5. Defeat the spirits
The sarcophagus was empty. And now the room is swarming with spirits from Hell that want us dead.
Defeat all enemies.

After the fight, you will talk to Lacra again to summon the wisps one more time. Feel free to choose whichever dialogue options you want. The wisps will appear, point to the wall, and Lacra will eventually smash through the wall, uncovering a hidden cave.

3.6. Explore the hidden cave
Right when we thought we hit a dead end, we uncovered a hidden cave connected to Kallias's crypt. Could his research be in there?
You can either explore the first section of the hidden cave or head straight towards the opening leading to the next area. Lacra will spot something interesting inside and call out to you, urging you to come closer.

3.7. Check in with Lacra
Lacra has found something interesting, it seems. I should see what she's got.
Just approach Lacra and a long sequence will begin which, if you choose the appropriate dialogue options, will end with an intimate scene between Coen and Lacra.

Lacra found a mandrake in the cave, which can empower you by granting access to a new vampiric perk - Mandrake Ward.

- [eat the mandrake] - You will receive Mandrake Ward perk (Once per night, upon taking lethal damage, regain 3 health segments) and you will be able to romance Lacra.
- I'm not eating that. - An angered Lacra will take the mandrake and leave the cave, which will end the quest.
If you eat the mandrake, Lacra will do the same. During the conversation with her that follows, choose several key answers - [follow Lacra] > [drink] > [kiss her] (1 Time Segment) - and this will lead to a scene of vampiric intimacy.

Before you leave the cave, check out the chest located near the place where mandrake was. Inside you will find a Witchcraft Manual and an Astral Talisman.

4. Ending
If intimacy occurs between Coen and Lacra, you will receive Mesmerise (Lets you mind control a target and forces the enemy to fight on your side) automatically; otherwise, you will receive a Phial of Lacra's Blood that unlocks it when consumed.
If you eat the mandrake and absorb its power. Reward: 1,000XP, Skill Point x2, Mandrake Ward (Once per night, upon taking lethal damage, regain 3 health segments)
We found a mandrake in Kallias's lair and absorbed its power. It might prove key in whatever awaits us next.
If you refuse to eat the mandrake. Reward: 500XP, Skill Point x1.
We found Kallias's lair and a mandrake growing within it - Lacra absorbed its power, but I wanted nothing to do with the grotesque growth.