Given the limited detail you given us, here's some stuff to write about while the kid is possesed:
1. the kid whos possesed keeps playing with the ooige board and keeps bringing in more spirits to the real world
2. the kid keeps doing things related to child who died in the house eg if a kid was drowned in the bathtub or something like that, the possesed kid pretends to drown his toys while taking a bath and says things the dead kids mother said while she drowned him
3. he acts normally but his friends start acting strangly and it turns out he was possesed by a spirit and the other 2 demons, so he's protected
4. the boy begins talking to an imaginary friend that tells him to do stuff so the spirit can finally be at peace eg on his way to deliver a letter to a girl he liked, the person was killed, so now the spirit wants the kid to find the letter and deliver it
That's all I can really come up with. You don't HAVE to use the examples I've given you, they're more used to explain the point I made.
1. the kid whos possesed keeps playing with the ooige board and keeps bringing in more spirits to the real world
2. the kid keeps doing things related to child who died in the house eg if a kid was drowned in the bathtub or something like that, the possesed kid pretends to drown his toys while taking a bath and says things the dead kids mother said while she drowned him
3. he acts normally but his friends start acting strangly and it turns out he was possesed by a spirit and the other 2 demons, so he's protected
4. the boy begins talking to an imaginary friend that tells him to do stuff so the spirit can finally be at peace eg on his way to deliver a letter to a girl he liked, the person was killed, so now the spirit wants the kid to find the letter and deliver it
That's all I can really come up with. You don't HAVE to use the examples I've given you, they're more used to explain the point I made.