need help with Scáthach and Cú

this is a really hard fight for you, these are challenge quests (note the level is 90++, meaning it expects your servants to be average 90 or to at least have a viable strategy) I'm not saying its impossible for you, but it really is an uphill battle. You're going to need to coordinate with support. find a support with MLB white rose and try to make sure you can 1 shot both of them, baring that, mashu is a good tank for their NPs if you have her skills up, but judging from her level you probably haven't had a chance to clear camelot yet. If you have any sure hit CEs that can help out too, but really you're gonna need a support or see if you can invest some fast XP into your cu. Chloe is a really bad choice for this fight I'm afraid.

I do have one, but do you have proper supports specially offensive ones? Also I suggest running the basic chaldea mystic code for huge attack buff, did you level that? If you have those then I'll be adding you.
I have an NP 3 Altera which finished this duo in a single turn with proper buffs. You just need to reduce shishou's health down to 500k by the third turn and you're set with the NP.
Just say so I remove people after 7 days of inactivity tho.
Well, but honestly you don't really have to do this
This is challenge quests are for people who has those level 90s who want to test themselves honestly and the level recommendations are even level 90 plus, but it's your choice.

You can borrow my Altera with the MLB event CE if you still need her :)

My IGN is Alexandria
My ID is 891,224,367