Dagannoth, known as Daggermouths to the Fremennik, are sea monsters. Many are found near areas inhabited by the Fremennik, who hunt them for their skin, which is used to make armour. There are many types of Dagannoth, the most powerful being the three Dagannoth Kings.
Dagannoth are assigned by Chaeldar, Sumona, Duradel/Lapalok, Kuradal, and Morvran as Slayer tasks. As such, you must have a combat level of at least 75 to be assigned Dagannoth as a slayer task. The Balmung (as well as its upgraded form), released with the quest Blood Runs Deep, hits them very hard, similar to the effect of using Keris on Kalphites or Scabarites.
Little is known about the origins of the dagannoth species. Dagannoth are first documented in Third Age where they started attacking the Fremennik, causing great losses to them. The Fremennik people battle them to this day.
It is unknown how the Dagannoth are organised, though it seems to be extremely similar to Kalphites; if the present queen dies, another one will quickly take its place. This is shown in Blood Runs Deep, as another Dagannoth queen appeared when the last one was killed. There are also the powerful Dagannoth Kings, though it is unknown what role they play. The dagannoths seem to be far more organised though, as the Kalphites have don't seem to have any interest in taking over the world.
Through the Spirit Dagannoth they reveal their goal: To force the entire surface world to be plunged into the Deep through a terrible flood, the event is called "The Day of Rising" by the Dagannoth. The lucky ones will be consumed first by the Dagannoth while the others will drown before they are also consumed.
There are several types of Dagannoth, which vary by level, location and occasionally name. For information on a specific type of dagannoth, see its article.
- In the FunOrb game Armies of Gielinor, one may summon a Dagannoth, which uses the appearance of a Spirit dagannoth.
- Dagannoth may be based on the Deep Ones from H.P. Lovecraft's The Shadow over Innsmouth. In the aforementioned story, they worshipped the elder beings Father Dagon and Mother Hydra.
- While the idea for the creatures characteristics may derive from the above mentioned, the name itself seems as if it may come from one of the first computer role-playing games, Dungeons of Daggorath, produced by DynaMicro in 1982.