Perhaps the first and greatest tribe in Grendel's Cave. They started out in k6.
Founding Members:
Diabolic
Pang
Silver Syn
Cain
Other Members of Note
Karina
JT
Their early exploits involved invading the odd smaller neighboring kingdom, pillaging, slaughtering and taking out Grendel.
The Demon Clan lasted in essentially the same state for longer than probably any other Clan in GC history, existing from early 1999 until recent times in some form or fashion. This has much to do with both their dedication to the game at it's original height, and their alliances with long term players such as Eclipse and Spiderman. Although never members themselves Eclipse and Spiderman both played vital roles in the founding and maintaining of the Demon Clan as life long allies of the upper echelon's of Demon Clan members.
The Demon Clan's final in game days consisted basically of weathering the hacks as best as possible. Being high profile many of their thanes were hacked or deleted and it was during this time that some small in-fighting began between the lower members and the higher members. Ultimately the DC dissolved their in game clan in favor of being remembered well instead of having to deal with all the crap that was going on at the time.
In recent times, re-founding of the Demon Clan has been attempted by Oni, Jt, and Thorin, however their leadership was never established in such a way as to give their claim any real substance. Of those previously mentioned only JT was ever actually a member of the Demon Clan.
As a side note, Cain was eliminated from the group at some point as he was essentially seen as a leach. He went on to join Outlaw King's Renegades.