|Appearance||House Hunting (mentioned by Beatrice Benson)|
Paimon is a demon, and one of the Kings of Hell who serve as Lucifer's henchmen. Paimon was worshipped by a Satanic cult (consisting of Carl and Joy Benson and several others), who evoked him circa the 1960s. When the cult evoked him, Paimon agreed to grant them knowledge of all the mysteries of the world, in exchange for one of the Bensons' unborn twin daughters as a human sacrifice in ten years. In the 70s, the Bensons and the cult murdered Ramona and sacrificed her to Paimon per the pact. It is unknown what happened to Carl, Joy and the other cult members afterwards; but according to the remaining Benson daughter Beatrice, it apparently didn't end well for her evil parents.
After Ramona was sacrificed to Paimon by the cult, she became a dark and powerful paranormal entity embodying all the death and evil that occurred in the house over the years. Ramona was ultimately destroyed decades later, when Aidan Waite burned the house down to put a permanent stop to her.
More about Paimon in literature can be found at Wikipedia.