This is a "Heritage" quest that you can get at level 31. It starts in Nektropos Castle. A major trick is to zone in and out of Nek Castle until the Swinelord and Billy is up in the Chapel (it saves having to clear and wait for the repop of both spawns). You will need to do the following quests near the zone line to get into the Library:

The Boar's Head
1. Head back to and cross courtyard to other side and enter door.
2. Head north and enter the next room (dining room) and put the eye in the boar's head on the north wall.

The Red Marble
1. Head South and enter the next room past the courtyard corridor.
2. Inspect the crate to receive a quest (The Red Marble)
3. Head back to the boars head near the Chapel and inspect it.

1st Floor of Nektropos Castle
1,2,5. Billy 3. Swinelord 4. Assassin

The Crate that starts it all

Billy everywhere!
1. Use this guide to get to the wine cellar
2. Examine the crate (-25, -25, -25) in the left wine cellar.
3. Head to Elise's Bedroom (SW room on 2nd floor), head downstairs and kill Billy.

Billy in the Chapel

4. Head to the Gameroom and kill spawns until you spawn and kill Billy.
5. Head to the Chapel and kill spawns until you spawn and kill Billy.
6. Head back to the 2nd floor and East to the library (if its locked you need to head do the Boars Head* and Red Marble quest). Open the bookcase to get to a secret area. Inspect the book leaning against the coffin (grab Legend and Lore: Fairy if you don't have it already).
7. Head through door in Library and jump down to the courtyard and Billy will spawn once more. This time DON'T kill him! Hail him.
8. Give him 5gp and he will tell you about the Frogluk.

Frogluk!
1. Go to the jail (East and then South of the zone in) and hail the Froglok Assassin.
2. He wants to be soothed with killings... hmm. Head back to the library and read the scroll in the hidden area.

Soothe the frogluk
1. Fiendish blood is obtained from Lamia (level 35^^ Group) which will spawn when you leave the library.
2. Kill 21 Nyth dolls (East of Elise's room then North).

After zoning in and out 10+ times he was finally up

3. Kill the Swine Lord (Level 32) in the northeast room in the zone courtyard.
4. Head back to the froglok assassin and hail him.
5. You know need to find and kill Malthus Everling (level 40) and inspect the chest in his room. To get to him consult the Getting to Everling Guide again.

Final Reward:
Guise of the Deceiver
Effect: Guide of the Deceiver (turns you into a Dark Elf).