First post on this forum here. So my character has over 100 in illusion magic but is not a master. I've slept to level up and all that but i still remain just an expert in illusion. I went and gave the master trainer 10 welkynd stones but she says she can't train me any higher. Im quite a noob at this game so i'm probably missing something very easy and obvious but i could really do with some help here. Thanks for reading.

Hmm. . . is your illusion fortified somehow, like by enchanted items to get it to 100?

Acadians right its most likely a fortify effect, check to see if Illusion on the skill menu is in green, or the last page in the magic menu for the list of active spell effects on you.
If so disrobe all items you're wearing check if this set everything back to black, if not and if you are a vampire this is most likely the cause.
Not 100% sure but I think the only way to level it up is to cure the vampirism if infected.

I literally love you guys - my vampire attributes coupled with my black hand robe and hood increased my stats. Thanks.

So glad you got it sorted out! Oh, welcome to the forums! :icecream: