Hi to every person that might still use this forum!
While rereading the trilogy, something came to my mind: In PG Makepeace singlehandedly summons Nouda, an extremely powerful higher spirit without using an special Item/Artifact. To me this sounds extremely impressive, since it is told that even getting a Marid under control can require up to 4 Magicans.
Maybe the process of summoning is easier when you want to fuse with the Spirit (I've read something here that the Afrit Jenkins summoned wanted the fusion to happen and so she ignored his mistakes).
But despite this, Quentin Makepeace seems to have immense knowledge and power, he seems far more powerful than most of the other Magicans of his time. Overall, there's little known about his character, where he comes from and so on.

Hey there! So I don't remember much about him summoning Nouda in PG, but I think I recall him having some help, like a group ritual with the rest of his accomplices.
As far as marids go, they usually take at least 2 seasoned magicians to summon, but it IS possible to summon one on your own if you're exceptionally powerful - look at Mr Button (PG), Khaba (RoS) and... Nathaniel. I remember Stroud saying somewhere that Natty boy could probably try his hand at summoning a marid on his own if he ever wanted to, and the kiddo kind of died before we got to see the full extent of his powers, so I wouldn't be surprised if he would've grown up into the most powerful magician of his time.