This battle is simple enough if you have a team of Sabers. As usual, build up your NP here.
This battle is way trickier. You have to choose between having two Berserkers pile on your team, or having a high HP Jack the Ripper act multiple times per turn.
Most known Sabers tend to be female, and Jack is pretty effective against them. In addition, her high HP combined with her tendency to dodge or remove buffs might make even using Casters take very long to defeat her.
Strategies and Recommended Servants
Don't depend on Casters to deal damage to Jack, her HP is near 1 million and it would take long to defeat her. Even Xuanzang, who's usually powerful as a Buster Caster might be less effective because she is a female and more susceptible to Jack's NP.
A Caster that can reduce enemy NP bar can be useful since Jack only needs 3 turns to charge her NP.
On the other hand, with more time having passed, powerful male Sabers became viable in this (except Siegfried, since Jack is no dragon). Saber Lancelot can charge his NP quick enough for a powerful strike, while Yagyu Munenori can remove Jack's buffs while keeping up with the enemy. Those who are limited to lower-rarities can depend on Caesar for the male Saber needs.
Note that Jack's NP affects female, and apparently, Chevalier d'Eon is not listed as a female. Therefore, you can count on d'Eon to become a tanking Saber in case of Jack unleashing her NP.
If all else failed, you can count on Mash Kyrielight for tanking, disregarding her being female, at least she could tank properly or grant invincibility to bypass Jack's NP.
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