What if the magic my character used was summoning or necromancy? There doesn't seem to be any of the categories presented they would fit into. I know this world has next to no restrictions about magic, but I just wanted to be sure before I make a character.
Summoning is a spirit magic. Necromancy is very common in Thanatos. As far as limitations go, there really isn't a defined set of limitations. You set your own caps, so it can be really easy to make an Overpowered character, but you will find that OP characters can be really hard to write engagingly. Trust me, I have more than a few "dead" characters because they are so op that they just aren't interesting.
Hope this helps!