Below are the phases of the boss:

1. Phase 1 is the simplest, it will mainly attack from a distance with little damage and AOE. No need for big dodging.
2. Phase 2 is more complicated, it will have more damage with a CAC + range weapon, and a big AOE. Do not hesitate to dash in the AOE which covers the map, because it never hits twice in the same place.
3. Phase 3 is the most complicated, a lot of AOE, big damage. Avoid ground explosions at all costs and roll to avoid the ring of fire.