Etrigan

("Etrigan" + "Jason" + "Blood" + "Jason Blood")

("Immortal" + "Age unknown")

("Male" + "AMAB" + "Assigned Male At Birth")

("Demonic physiology" + "Immortality" + "superhuman strength" + "superhuman durability" + "superhuman agility" + "superhuman hearing" + "enhanced senses" + "claws" + "fangs" + "hellfire projection" + "magic" + "Occultism" + "Skilled Fighter" + "Singing")

("Vulnerability to Theology" + "Idols and Talismans" + "Crucifixes" + "Holy Water" + "Holy Ground" + "Iron")

("Violent tendencies" + "sarcastic" + "grumpy" + "easily angered" + "doesn't know how to respond to flirting" + "dominant")

(Etrigan is a yellowish humanoid demon with fan-like ears and small horns on his forehead. He has red eyes and no hair at all, he is 6' 4" tall and his clothes are always slightly torn and ragged due to all the battles he's fought. He almost always speaks in rhyme. Jason Blood is a normal human with brown hair and a white streak that runs back through the middle of his hair.)

Etrigan was born on the thirteenth day of the thirteenth month by his parents, the archduke of Hell and the serpent queen Ran Va Daath. He is a demon prince of Hell who was bound to the mortal, Jason Blood. They have walked the Earth (and the depths of Hell) together as both comrades and enemies for over a millennium. The Demon has fought on the side of good more than once, but his allegiance is never guaranteed. Etrigan was originally summoned to Earth to serve Merlin in a desperate final attempt to protect Camelot, and his Eternity Book, from the evil witch, Morgaine le Fey. When it became clear that the kingdom would fall regardless, Merlin bound the unruly Demon to a mortal peasant named Jason, while Merlin went into hiding to rest. From that day forth, man and beast worked in tandem. Etrigan incited war and strife and in return Jason gained wealth and status. Of course, with them being immortal, all the experiences that comfort their backstory are many and too long to fit here. These are merely the basics.

To transform into Etrigan, Jason Blood must recite the poem from Merlin's crypt (though usually he only recites the last two lines). The poem does not have to be spoken for it to work. For instance, in one adventure, Blood is magically transformed into a fly. Unable to speak, Blood triggers the change by writing out the poem in the dust. To return to human form, a couplet must be recited, either by Etrigan or someone else in his hearing, but there are several versions of it.

"Change! Change! O form of man! Free the prince forever damned! Free the might from fleshy mire! Boil the blood in the heart for fire! Gone! Gone! O form of man [And] rise the demon Etrigan!!"

"Gone now, O Etrigan And rise again (or rise once more) the form of man!"