Magic centered freeform concept
I am a long time player and dm/gm of several different systems, but I have had a character and story idea in my head that ultimately I think may work best in a freeform environment. I'd like to play a young but powerful magic user that explores the deeper, riskier, and more unusual aspects of magic. Summoning, planar travel, dealing with otherworldly entities, mind magic, etc. higher levels of magic that are often not reachable or not really explored in games like D&D.
I think, with the subject matter it might best fit into an adult, or at least mature, game. I don't really like a story line focused on a character walking the road to personal destruction, so a totally dark and serious game may not work well. I would be willing to go a bit into a more light-hearted realm, to some degree, since I envision a character that is more socially inept and exploring magic that might put him in many unusual and unexpected situations. So probably something leaning toward the serious side but not totally gritty.
I don't know if this concept would fit into a pre-existing game, or a game be made for it. I don't know if it would be best for a small group, or a solo game, but I am tentatively open to any option.