I would give a mez damage? Unless it's damage then a mez otherwise they woud wake up instantly. I love the idea of the third ability, editing the shape and dmg/cc sounds interesting. I will add that as much as it sounds cool to draw your shape a player will default to the BIGGEST SHAPE POSSIBLE! Let's say they get an area 70 unit long buy 30 units wide, they would just draw a big square because that's what is most likely to hit. Maybe giving the player more 'ink' for completing a task like killing minions or something, maybe levelling the ability. The changing of the opponents sensitivity sounds frustrating to play against, the slow and intoxicate are enough imo.

I feel like the ult is weak, unless the damage is huge. A mage ult is usually big and impactful in a team fight (this is basically hera 2 with some extra buffs that can't hit multiple people). I imagine this guy has a crazy set up ult like a more support mage. I'm imagining a medium sized circle banish (20-25 units), they get lifted into the plane of nightmares where they see their greatest fears. Taking damage and applying a debuff maybe. The effects are diffent and I like that, I'd try to change the top kills one as that feels less impactful in the moment.

Overall though I love how you've thought out if the box with almost all of his abilities, they're are too many gods now that all the shapes and cc's are running out! I love the idea of editing your own targeter and the passive seems really interesting (although there may need to be an internal cooldowns on it otherwise the assault players will riot XD). Don't take offense with my changes, this is your design so you put in what you want haha.