T.A. 1994 Dúrin's folk found large silver deposits in the southeastern Ered Mithrin, greater than any ever found in Khazad-dûm. This later became known as Thundercleft, one of the larger mining colonies in the Grey Mountains.
In T.A.2563 the dwarves were taken by surprise by the Dragon Khuzadrepa who unleashed his vile spells against them with terrible effect. Few survived his furious assault, which was swift and deadly. The sack of the city complete, he looted the ruins and piled the wealth of the Dwarves into a mound in the hall of Dúrin. Not content with Thundercleft's treasure, Khuzarepa sought more, roaming his territory in the Ered Mithrin chain.
Other Hands, issue 23, from 1998 - article: Dragons of the North:
- locations of the Silverpit and Thundercleft are swapped in comparison to current location.
- Thundercleft has been named as Zeleg-ubraz (Kh.Gold stair)