The servants of the underworld are powerful but unable to reach the mortal world by themselves, but that can be easily solved by the summons, servant willing to open portals from where the demons can raise and take from. Unfortunately most times this portals damage the demos so they must posses mortal bodies to strengthen themselves and hide their presence, but this process requires the mortal to suffer changes in most occasions. This demons are bound to relics created in the dark forges, such as wands or rings that allow to control the beast, this are given to the summoner making the possessed bodyguards or pets to the summoner.