To use the ancient cavern, one must have completed the first part of barbarian firemaking training, and then talked to Otto about pyre ships. After the conversation is over, the player can now go in the whirlpool. Upon entering, one must climb down stairs and then run south to a set of stairs leading up to the mithril dragons.
The whirlpool entrance is closer to the stairs and only involves running past brutal green dragons. However, its drawback is that players cannot have a familiar summoned when jumping into the whirlpool, which wastes an inventory space for the pouch. Many players therefore prefer using the fairy ring or a ferocious ring.
To access the ones in Brimhaven Dungeon resource dungeon, the player needs to wear the Daemonheim Aura 4, obtained from the elite set of the Daemonheim tasks, the area is located on the other side of the cave, through a magical barrier. This area contains 4 dragons.
During the fusing of the dragonkin key, the mithril dragon temporarily appears as level 150.
In a Postbag from the hedge, Oziach pointed out that there are bronze dragons, iron dragons, steel dragons, and mithril dragons when he was chatting with Evil Dave. Oziach deduced that there will be adamant dragons, rune dragons, and even Dragon dragons.
When killed, it says on the Adventurer's Log: I killed [number] of mithril dragons. If you killed 1, it would be "I killed a mithril dragon."
Their examine text indicates that metallic dragons, or at least mithril ones, may be the result of unnatural experimentation; of course, this may also refer to how they were created by the Dragonkin. With the release of the quest One of a Kind, this has been confirmed.
Mithril dragons are the only metallic dragons that do not drop the dragon platelegs and plateskirt.