It's not the first time that Illya decided to solo against Surtr Fenrir, on top of that I activated Illya's NP from the Archer Class.
I used Baobhan Sith because its NP was at level 3, Atalanta, Emiya and Sigurd, and also Angra Mainyu to reduce Surtr's NP.
You're doing really good Bageko, even at 6/6/6 NP1
So her arrows got even more brutal
Sutr supper recollection quest
NP1 Muramasa, Black Grail CE lv 20/20, and using his 2nd skill right when they put up evasion