Feral

To be feral is to be completely unhinged from reality. Feral demons forget who they are, who their friends and family are and only live for bloodshed and mayhem.
Only demons suffer from this ever present state and the average person can keep feralness at bay without any effort at all. However, strong rage and devastating emotional damage can bring feralness to even the most steadfast of demons. Once feral it is next to impossible to bring a demon back to themselves. Only exceptionally powerful healers can mitigate some of the symptoms, but not cure it completely. 
The only demon ever to have been cured is King Lucan. In order to achieve this miracle, a powerful healer sacrificed his life by using every drop of power he possessed and it was enough to drive away the King's feralness. 

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Taran, one of the brightest demonic minds who embraced human advancement, found a cure for feralness with the help of a powerful healing serum (designed to speed up an immortal's natural fast healing), the Angelspear and in cases where the feral demon is too powerful, their blood.