Why Euryale is so important to camelot?

Because of the bosses that happen to be sabers and also males. Euryale deals extra damage to males with her NP, has the potential to charm lock and has good np gain, so she can spam her massive damage farily often.

the mini nutcracker is ideal for the many saber class servants who all have balls she can bust and if I'm not mistaken they're also all earth attribute meaning she has even more sack-slapping power. she has x2.1-2.2 effectiveness on the enemies with an easy to charge NP that deals a baseline 1350%-1450% on males and gimping their attack.

She isn't really needed for Camelot, but she can make stuff that is difficult less difficult due to her anti-male niche.

Rather than saying Euryale is very important for Camelot, it would be better to say that she is your ticket to make your life easier in Camelot as her niche is actually working very well against mr praise the sun. Tbh, what you need in Camelot is not Euryale, but your ability to make a strategy to fight your opponent as your opponent now have gimmicks and not a straight forward battle like before. Camelot is famous for weeding out the weaker player that only relies on brute force and the stronger player that actually use their brain to fight against their enemy.

She is not important, lol. She is just part of Camelot easy mode along with Sumanai, Modred, Herc, David, Shiki and Ridertoki.