|Release date||1 February 2011 (Update)|
|Main music||Courage, Dark|
|Strongest monster||Revenant dragon (level 126)|
|Inhabitants||Dark beasts, Dragons, Demons, Hellhounds, and Revenants|
The Forinthry Dungeon is a very dangerous cave that ranges from level 18 to 32 of the Wilderness. It is a refuge for dragons, many kinds of demons and even the vicious revenants after being forced underground by adventurers in the year 169 of the Fifth Age. The dungeon is named after Forinthry, which is the original name for the Wilderness. The dungeon is extremely dangerous because not only are the revenants a lot more powerful than their combat level suggests, the cave is also a dangerous PvP area. There are player killers who travel in teams and cause heavy damage quickly. Higher levels in members' worlds are known to use Smite or Soul Split to reduce your prayer points, so do not bring items you are not willing to lose. Use Protect Item if players are in sight and bring an emergency teleportation item.
The dungeon also plays a small role in the quest One of a Kind, where the player visits the green dragon chamber to investigate for mysterious markings.
The dungeon has two entrances from the Wilderness.
- At level 17 Wilderness, east of the Bandit Camp and Dark Warriors' Fortress and west of the south-western Wilderness Volcano steps. The Wilderness sword 2 provides free infinite teleports here, and it is a short run west from the Wilderness Lodestone.
- At level 31 Wilderness, south of the bandit camp mining site, and east of the Forgotten Cemetery. This entrance is more dangerous due to a prolonged period of time spent walking there, unless the player has 57 Woodcutting to create a Waka Canoe.
As both entrances force you to walk through the Wilderness, one must be wary of player killers.
Revenants are slain monsters from the Third Age, and are the main attraction of the dungeon due to their valuable drops. All revenants can be found in the northeastern chamber, although the dragon will not appear on free worlds as it is a members only monster. The revenants were banished into the dungeon after players reclaimed the Wilderness from them in the Fifth Age. Although considerably weakened, they are still pose a threat to passing players.
Five green dragons can be found in the southeastern chamber, and are one of several places in the Wilderness where Green dragons may be found. There are five spawns around a pit. They only appear on members worlds, as they are a member only monster, and thus, do not appear on free worlds.
Lesser demons can be found in the western/middle section, east of the ankous and west of the hellhounds.
Greater demons can be found in the south-western sector. There are nine spawns of greater demons and they are rather clumped up, allowing for decent kill rates, although the danger of the Wilderness makes killing them here unfeasible on a slayer task, as Kuradal's Dungeon has a relatively similar amount of spawns and is safer.
Hellhounds can be found in the center of the dungeon. There are six spawns fairly scattered around a large pit, and along with the Wilderness Volcano, the only places where free players may fight hellhounds.
Dark beasts can be found in the westernmost chamber of the dungeon, replacing the Ankous who used to be there until 8 August 2016. There are 9 spawns in the cavern, and as they are members only monsters, will not appear in free worlds.
- Revenants were originally the replacement for Pkers between 11 December 2007 and 1 February 2011. They could attack you depending on your combat level and depth in the wilderness (just as Pkers can today) as well as teleblock and freeze you.
- The dungeon was released due to complaints on the Bounty Hunter system, and Jagex created a poll asking if the players would like to have a new home for the revenants, or let them roam the Wilderness as usual.
- The unique gear the revenants drops used to only be obtainable from PvP and Bounty Worlds which were removed when the old-style Wilderness was reinstated. The only other place to obtain such gear is the Chaos Elemental, but it is much riskier because the Chaos Elemental is more dangerous, resides in much deeper Wilderness and is solitary.
- Despite the description of several monsters being "banished", you can still find them in the same places. (e.g. Hellhounds in the Wilderness Volcano)
- Surok Magis's hideout can be seen from the northern entrance of the cave with an orb of oculus.
- From 00:00 UTC 12 November 2011 to 23:59 UTC 14 November 2011, there was an event where members could gain double loot from several dungeons, including the Forinthry Dungeon. This was part of Jagex's bot-busting celebration.
- Forinthry Dungeon received a graphical rework on 19 September 2016.