Note: This is a hidden mini-quest; you do not get quest points for it - though you still get a reward!
Start Point: Talk to the Khazard General east of Relleka Requirements: Must have completed the Fight Arena Quest, Amulet of Ghostspeak (obatined during the Restless Ghost Quest), Ring of Visibility (obtained during the Desert Treasure Quest); must be able to defeat a level 160 ghost Hell Hound 'Bouncer'
To start things off, head to Relleka and walk east till you see the ghost of General Khazard. Remember him, the crazy chap from Fight Arena? You must be wearing your amulet of ghostspeak and your ring of visibility to see him.
When you find him, speak with him. Make sure you don't say that you remember him from anywhere. He will ask you find Sin Seer, an old chap in Seer's Village.
Head over to Seer's Village and climb to the top floor of the house with the spinning wheel.
Talk to her, and, being the stubborn old hag she is, you'll have to bribe her with 40gp. She will hand over a report to give to General Khazard.
Bring the report back to General Khazard. He will ask you to find four of his scouts and give them the following message: "The planets are nearing alignment; we will meet in the place of half light and ice soon. Beware of others, for though they are weak and few, they are cunning." Head out to each scout and give him the message.
Scout
Location
Outside the front of the Gnome Stronghold, near the apple orchard
Between Falador and the east side of Draynor Manor
Southeast of the Shantay Pass
Southeast of the Teak and Mahogany area in the Tai Bwo Wannai Village
After that bit of fun, head back to ol' General Khazard. He will ask you to go to a 'fish-men cave' - the Goblin Dungeon, southeast of the Fishing Guild. He'll hand over a severed leg to use as a key. When you are in the cave, head northeast till you find a crack.
Choose to open the crack, but only if you have equipment to fight the upcoming level 160 hellhound 'Bouncer'. You will not be able to use prayer. Anyway, head in, where you will be greeted by said ghostly Bouncer, level 160.
When the ghost has very low health, you'll automatically throw the severed leg to distract the monster and deal the finishing blow.
Congratulations! Mini-Quest Complete!
Rewards: Ghostly Sword and 2000 Slayer Experience
The Shadow Sword may not be the best sword, but goes nice with Ghostly Robes.