They probably had a real spell but since none of them had any magical power it always failed to work but it worked for the MC since he had Solomon's ring
I figure this out because if you look closely the ring lit up after he finished chanting.
@AthalosJ
I don't think it was so much magic as having nothing that could hold a contract with a demon since the ring holds 72 contracts it technically could have summoned anything well maybe
And today the MC learned an important lesson:
When you are truely involved into the occult NEVER go to an occult research type of CLUB!
You will not find any people truely involved into the occult themselves in such a club.