"What is Hell, but the total abscence of hope? The substance, the tactile proof of despair?" ~ Ken (giving an insight into his warped philosophy)
Ken was the chief antagonist of the Buffy episode "Anne" and disguised himself as the owner of a Family Home designed to lure vulnerable teenagers into his grasp before he and his minions kidnapped them and put them to work as slave-labor in a large factory situated in a hell-dimension.
Ken was the apparent leader of a group of demons that had been luring runaway teenagers via the Family Home for years, offering aid to them only to enslave them once they came to the home and toss them into another dimension were they would work as slaves until they grew too old to work, at which point they were returned to the earth realm to be tossed into the streets to die.
Ken's dimension worked differently from our own and what seemed like decades for his victims was merely hours or days in the real world, this meant his victims aged incredibly fast - so despite only being enslaved for a few days the effects of the dimension would age them all the way to old age.
Buffy encountered Ken while she was running away from Sunnydale, going under the guise of "Anne" - she tried to infiltrate Ken's organization but failed, ending up sucked into the hell-dimension as she tries to save Lily, a teenage girl she had befriended on her travels.
Buffy fought Ken and his guards until Ken gained an upperhand on the Slayer via holding Lily at knifepoint, yet the demon fell prey to arrogance as he wasted time taunting Buffy - allowing Lily to knock him over the side of the platform: Buffy then attempts to flee with the other teens out but has to hold up an iron gate that has began to close - this allows Ken to attack her but his clumsy attempts to harm her only result in him getting impaled on the spikes of the gate..