If Androxus uses his Reversal (he will), use your just before he attacks you with it, then Whirl to go right behind him. If he isn’t pro, he’ll get confused: you can take advantage of that to finish him off.

Seris is really strong against Grover in general: just creep up behind him using your shadow travel and attack him from behind. His damage will be lower, as you will be at close range.