Requirements: Must be wearing the Ring of Visibility from Desert Treasure and an Amulet of Ghostspeak from the Restless Ghost Quest.
Start: Go to Glarial's Tomb just west of the Fishing Guild and talk to the Mysterious Ghost there.
Listen to his story. He will give you the Ghostly Robe (top). He will also ask you to find a ghost named Rennard and will give you a clue to his location. There are 3 separate "sequences" that are defined by the first clue.
Regardless of the sequence, you will need to find the following ghosts in this order and will receive the pieces of the set as shown:
Kharrim: Ghostly Boots Lennissa: Ghostly Robe (bottom) Dhalak: Ghostly Hat Viggora: Ghostly Cape
The clues and your path:
Sequence 2 - mentions a thief being to the northeast Sequence 3 - mentions a thief being to the southeast (barren land, throws victims into the desert)
Rennard: Located by the Pirate Ship hidden between the Pirate Hut and Agility Course at the very top of the Northwest side of the wilderness. Very dangerous level 52 wilderness and potential PK area. Recommend you minimize the items you bring,but you need a knife to cut webs.
Kharrim: Located by Evil Altar just below the snowy regions in the western wilderness (Level 38 multi-combat).
Lennissa: Church on Island of Entrana, by the altar. Safe location, but remember no armor or weapons. Bring Glory amulet or Lumbridge teleport runes.
Dhalak: Wizard's Tower south of Draynor in the library on the first floor. Bring Ardougne or Varrock teleport runes.
Viggora: Second floor on the Rouge's Castle, far northeast of the wilderness. Very dangerous level 52 wilderness and a multi-combat area, potential PK area. Recommend you minimize the items you bring, but need a knife to cut webs.
Rennard: Found in the wilderness Bandit Camp (level 24 and multi-combat). The bandits can be bothersome and make it difficult to hear the story. This is a fairly safe location, but multi-combat, so keep your eyes open. Bring teleport runes and wear a ring of life.
Kharrim: Wilderness Graveyard of Shadows (Carrallangar). By the large grave on the west side. (level 19). The zombies can be bothersome and make it difficult to hear the story. This is a fairly safe location. Bring Falador teleport runes and wear a ring of life.
Lennissa: Port Sarim docks at the far south end of the docks, beside the ship used in the Dragon Slayer quest. A long walk, but a safe location. Bring Falador teleport runes to save on some walking.
Dhalak: Monastery (Prayer Guild) north of Falador. He is upstairs by the altar. You need level 31 prayer. Safe location. Bring ectophile or Varrock teleport runes.
Viggora: Slayer Tower in Morytania. He is on the 2nd floor not far from the stairs, before the infernal mages. You need to have done the Priest In Peril quest to head into Morytania.
Kharrim: Center of the wilderness lava maze by the ladder at the center of the maze. Very dangerous level 43 wilderness and a potential PK area. Recommend you minimize the items you bring, but need a knife to cut webs.
Lennissa: Near entrance to gnome ball field in Tree Gnome Stronghold. Bring Camelot teleport runes.
Dhalak: Upstairs in Pete's Party House near Seers Village. Safe location. Bring Glory Amulet for Edgeville teleport or Varrock teleport runes.
Viggora: Edgeville Dungeon (Paddewwa) at the very back of the earth warriors chambers, you need 15 agility to get in. This is fairly safe, but is level 10 wilderness. The earth warriors can be bothersome and make it difficult to hear the story.
Ghost Robe: +5 to Magic Attack and Defense Ghost Skirt: +4 to Magic Attack and Defense Ghost Gloves: +2 to Magic Attack and Defense Ghost Boots: +2 to Magic Attack and Defense Ghost Cape: +5 to Magic Attack and Defense Full Ghost Garments: +21 to Magic Attack and Defense
You must listen to the full story for each ghost.
You do not need to complete any combat parts of Desert Treasure to receive the ring, but do need the thieving level requirement.
You can get a replacement ring by talking to Rasool by the picnic area just south of Glarial's Tomb.
You can get a replacement Ghostspeak Amulet by going to the Shack just south of the mining area in Lumbridge Swamps.
You get more than one of each of the garments by dropping them and immediately asking for replacement from the various ghosts and them picking them up again. This works for the ring and amulet as well.
The garments cannot be traded.
The ghost garments are weightless.