Riverclan from the warrior cats series.
First series
Crookedstar is the respected leader of RiverClan, father of the well known Silverstream. When he is first introduced in Into the Wild, he is already elderly and fragile, but remains with a firm hold on reality. He organizes several attempts to steal back Sunningrocks but fails. In Into the Wild, Firepaw describes his twisted jaw to look as though it had been badly broken, and then healed incorrectly. While it is still a mystery as to how he received his twisted jaw, it is hinted in Fire and Ice that it was a souvenir from a battle.
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