First collect 6 poison sacks. You will find them by killing spiders under Kalak's statue in Caravan Way. You will need to by a square key at Trici to go there.

Go to Old Magda's, in Shadow Square. Chat with her, don't be afraid to refuse the mission that she might ask for. Rather, harrass her till you can propose to sell some poison bags. Don't actually sell the bags, but ask if she doesn't have some information and trade 3 poison sacks for it. She will tell you that there are some secret entrances to under Tyr, and that she has a key to go there. Buy that key for 3 more poison sacks. Don't be rude, she won't tell you what is it for...

Go to Friedla's in Caravan Way. Use the key on the large chest, you will enter a first area where you will find some Zombies. If you are kind with them, they will give you the second key.

Go to Mila's Inn in Caravan Way, and use that key on the back door. You will enter the second area where you will find some chest and wandering Sligs. Be persuasive with them and they will give you the third key. You can also look in the chest if you want to have some more mirrors or leather drums. Eventually, "look" at some of the skeletons that lie on the floor, this might awake some giant skeletons or skeleton warriors. Notice that skeleton warriors are highly magic-resistant and +1 or better weapon to hit.

Go to Rainikin's in Shadow Square, and use that key on the cabinet. If you dare, you will enter a area with some wandering Shadows. If you are friendly, they will soon drop the next key. At this time, don't fear to "view" and awake the skeletons , as they can drophalvesof a strange Golden key.

Next go to Katjana's, in Shadow Square, still. Use the key on the cabinet, and enter a place where you will find some nice Red Slaads, which will be of great help to your XP's. There are some skeletons to awake too, and a couple of chest as usual.... Get the last key (and maybe some parts of the golden key if you don't have the two halves already) and go to Dariya's in Shadow Square .

Head to the "Full Flagon", and ask Dariya if she knows a secret entrance under Tyr, and, surprise, she happens to know one hidden just behind some barrels in her own place... This information will cost you 500 cp, and likewise for each time you want to use it. Use the last grey key there, and enter this area. It's rather empty, except for some skeletons to shaken and a couple of chest to bash. Then cast all your defensive spells on and investigate the rubble barrier at West. You might find some narrow passage. Take it and enter the last area of this Quest... You will find some huge doors. If they are opened, you can just leave, somebody was there before you and had already taken the treasure. Come back another time, when the Quest is reset!

If they are closed, you will not really have time to admire the surroundings, as 6 Revenants will jump you. They have the ability to cause fear, so be courageous! If you survive that, you might want to open the huge doors. "View" them, and you will be proposed to use the parts of the strange key. If you don't have this option (if you have already joined the two parts of the key), try to bash or pick the doors, but it'll be very hard.

Whatever, the gates open, and you enter a large room where you will have the opportunity to destroy 3 Banshee Dwarves and 3 Obsidian Golems... Close to the last one, at the Northern end of the room, you will find a altar. First, take one half of the key, "view" it and "use" it to do a full key with the other half. Next, "view" the altar and use the Golden key, or just put the Golden key on the altar, and enjoy! You win around 1.666 Xps, and, more interesting, you find some magic item. Check your inventory...

Now you want to know why this quest is called the Bloodletter? Well, maybe you will find... Sooner or later :-)

Hints and Tips:

Each time you use a key for the first time, you will get around 500 XPs, depending on your level, except for the last room where you earn 333 + 1.666 XPs each time. Note that XP reward vary with levels. At low level you'll have 1.000 XPs for each door instead of 500, so if you start a new character give him all the keys, he'll score plenty of XPs even if he doesn't enter the rooms (just open the doors).

The golden key is wasted when you put it on the altar, so use it only if the quest was reset (doors closed). Otherwise you will get some minor item and 500 XPs...

Check carefully your "Current spell effects" before going through the rubble under Dariya's place. Be sure to have "Cloak of Bravery" (Lvl 4 Cleric/Druid spell). If ever you are feared in last room, don't cast Dispel Magic on yourself, it will remove all your magic and I'm not sure it will remove Fear...

Good luck :-)