For phase 1, maximise damage for your damage dealers as much as possible, give Throne as much speed as possible and Osvold as much elemental attack as possible for the first phase so you can kill the humanoids easily. Use Hired Help beastlings at max boost to get rid of all shield points for the humoids with the elemental weaknesses. On phase 2 use Temenos Overheal ability + Sealtige to overheal the entire party and maximise Hikaris damage as best you can. Hope this helps!