God Idea: Apep.

I feel everything about him is fantastic. If I did have to find something wrong, which I usually do, it's that his passive is boosting the wrong thing. I mean he's a bruiser with relatively high scaling, so the current passive may be a bit dangerous. I suggest that to keep the 'final struggle' feeling of the ability, it should increase defences by a FLAT amount for a small duration (6 or 7 seconds seems good). Note that the passive has to scale with level to be balanced. This would increase his somewhat lacking innate tankiness as a bruiser/ tank.

If you do want to keep the magical damage buff, make it last a duration and most importantly, make it flat damage. Percentage based abilities are a pain to balance out, and you can just make it easier for yourself by making it flat damage.

Also, I think he should e long range, I know you were goin more bruiser, but there I'd only 1 long range tank, and no long range bruisers.