Was afraid of the "Energise the spheres" phases because speed isn't really my thing, but he only did it once and I somehow did it anyway. Not too difficult overall (pro tip: don't facetank huge slams) although I was surprised by the tentacles' damage and had to dodge a bit more than I'd have expected.

Current (and final) build: https://pobb.in/Rbvvbg3iThYz