i knew about the secret boss but its second phase was a bit of a trouble with me so i just decided ''fuck it ill just spam my normal attack and use healing potions when im low'' and it WORKED!? yeah i was dumbfounded how i did it but fuck it im glad. W game. W designs and animations. kinda W secret boss.
The 2nd phase is piss easy, you quite literally just stand in a corner swinging the melee magic spell and you will dodge most of the attack. The dangerous fan-pattern attack of the boss can't even touch you lol