Acheron mammoths are a species of elephant-like creatures mentioned in 2004 in a Behind the Scenes article as a future update, alongside the Lizardmen and many other updates, most of which made it into the game. Although they have yet to appear in-game, a model was nevertheless made for them, although it was ultimately unused, only eventually appearing as a monster as part of Old School RuneScape's Wilderness Rejuvenation and first birthday celebration.
They inhabit the icy continent of Acheron, far north of the Fremennik Province, and make a small appearance in player-owned ports, as a Mammoth Head can be built at an icon hotspot. The Mammoth was also an option in a guaranteed content poll on 28 April 2008. It was a possibility for one of the future summoning familiars, although it was outvoted by the phoenix.
Acheron Mammoths will be introduced as elite monsters, as one of the four RuneLabs high level monster winners. They will drop ingredients for a new level 99 Summoning Beast of Burden pouch, baby mammoth.