The Vrack cult is found in a secret subterranean lair underneath the TOWN TEMPLE that is located at X:15 Y:76
To find the cult, go to X:20 Y:9 inside the temple. The south wall is false. Just walk through it.
Once inside the cult you can explore around a bit but here is a quick summary of the most important things.
You can meet a guy by the name of Seleron at X:11 Y:21
He asks you to find a key that he suspects a Vrack has stolen. Once you accept the offer to help him, you find the key at X:13 Y:15
When you return the key he will get angry because in order to recover the key you must slay a priest and that makes him upset. He vows vengeance. When you attempt to leave the cult area you will be ambushed by Seleron and a large force of demon spawn.
Seleron has a small hidden treasure larder. To find it go to X:8 Y:23 and search the west wall. Once inside the hallway beyond you will find a few magic items of small worth and a mirror. If you enter the mirror you will be teleported to a crypt of a resting Lich. You will not get to battle him but instead you find a bone mask.
If you go to the ITEMS screen and select the bone mask and click USE you will get a nice surprise. Prepare to select 3 PCs to challenge the Lich and two of his undead lackeys to a trial by combat.
