Castoria’s slightly unusual as ST Arts units go. She can work in conventional bursty setups, with two Caster Castorias and a damage-booster (probably Tamamo or Oberon), letting Berserker Castoria loop three times and hopefully clear the fight. Castoria isn’t bad at this, to be clear—at the end of the day, she’s an Arts Berserker with great loop specs, so if damage thresholds aren’t too high and/or she has niche damage, she might suffice—but she’s not the best at it, and the better alternatives are old enough and plentiful enough that there’s a good chance established players have at least one of them.
Where Castoria shines is in teams designed for slightly longer fights. Caster Castoria brings so much of value that you probably still want at least one copy of her on the team—and, in fact, might still start the fight with two Castorias and plug one of them out for a third support. Ultimately, Berserker Castoria still wants to clear fights as quickly as possible, even if going for a mid-range setup, so using plug to speed up the first few turns is probably a good play. You can also replace one of the Castorias with Cnoc na Riabh, who brings more overall damage—though her drawbacks are such that she’s probably not the best choice unless you don’t have better options. If you don’t have Caster Castoria natively, though, she can be a good choice for getting things rolling.
For your second support in the long-term, you want either Lady Avalon or Tamamo, and each comes with their own advantages. Both bring healing—important for offsetting inevitable chip damage—along with damage buffs and NP charge. Lady Avalon brings skill-based charge, overcharge (which can add damage for Berserker Castoria and helps Caster Castoria protect the team during off-turns), an emergency party defense buff (also good for off-turns), and crit tools to complement Berserker Castoria’s. Tamamo, on the other hand, offers cooldown reduction. That’s a lot more points in Lady Avalon’s favor than Tamamo’s, but CDR is massively useful for Berserker Castoria teams in particular, as those teams are much safer while Castoria is looping, and Castoria is probably only looping while everyone’s skills are active. A Lady Avalon team has more ways of surviving through dead turns, while a Tamamo team just has fewer dead turns.
Caster Castoria’s role in these teams, aside from providing charge and the like, is to use her NP whenever Berserker Castoria can’t. If you can save Berserker Castoria’s second skill for when Caster Castoria is ready to NP, you can get three hits of Solemn Defense for the party, which may be enough on its own to protect the team until all skills are off cooldown. Lady Avalon makes this even easier, providing an overcharge level with her Charisma and potentially another by using her NP before Caster Castoria’s, and Tamamo reduces the need for overcharge levels by virtue of effectively shaving a turn or two off the time Caster Castoria has to stall.
You can also theoretically run a Lady Avalon/Berserker Castoria/Tamamo team, which has more healing and gets the benefits of both Tamamo and Lady Avalon, in exchange for having less charge and a harder time surviving through dead turns. This is probably a weaker strategy overall, but it’s not a fundamentally unworkable one.
Castoria’s crit tools also mean she can potentially function in unconventional Arts teams pretty effectively. In fact, she’s actually something of a modernized Qin Shi Huang in a lot of ways, giving strong-but-imperfect party survival on her NP along with very good overall damage. It’s no longer really feasible with the way content has scaled, but I used to quite like running Lanling/QSH/Sherlock—it was a durable, crit-focused team where everyone was able to contribute and the kits synergized nicely. You can mostly swap QSH for Castoria and have a similar-but-stronger setup, bringing a lot of the same advantages, but with an actual damaging NP to fall back on.
Castoria’s a super self-sufficient unit, so if you don’t have the SSR supports, you can still get use out of her with lower-rarity Servants. Mozart and Mary Anning are both solid low-rarity Arts supports. Mary Anning even brings exactly enough charge to let Castoria NP turn 1 with a CE like the Black Grail—between Mana Loading and her own batteries, Castoria has 90% charge, so a tiny bit of extra charge gives her immediate NP access. Barti also brings exactly this much charge, and while he’s usually thought of as a budget Quick support, his buffs are actually type-agnostic and work well with Castoria. Barti brings crit buffs, too, and he makes it pretty easy for Castoria to crit on turn 1—something she doesn’t usually get to do unless you’re running Mozart.
As a final set of options, Xu Fu and Hans are also good picks. Both bring crit damage up and stars per turn, and around the same amount of overall damage push. Xu Fu is better if you need a bunch of charge all at once—say, if you don’t have Mana Loading and need 30% charge turn 1 to let Castoria NP immediately—while Hans is better if you want to prioritize Castoria’s crit damage potential or don’t have a way to get Xu Fu an immediate NP.
It's also worth noting that Castoria is a single-target Berserker with massive self-charge and situationally very good damage, which means she’s potentially useful for dual-core farming setups for 90++ nodes. She can even splash some of her charge to an ally, making the setups that much more flexible! Castoria will be particularly good for nodes that have a single enemy on wave 1 or 2, as Castoria will likely be able to drop the solo enemy on the early wave, and then NP again on wave 3 to help reach damage thresholds on the highest-HP enemy. It’s very similar to the things that make Hephaestion a good farmer, and her damage is even pretty comparable.
The Black Grail is definitely Castoria’s best CE, as it helps offset her lowish NP damage, Castoria isn’t really built for super long fights anyway, and you’re likely running her with someone who can heal off the demerit. There may be situations—particularly when farming—where a starting charge NP is more valuable for looping reasons, but Castoria has such easy NP access this will rarely be the case.
Crit damage CCs are a great pick for Castoria—she has easy crit access, and while she does have some innate crit damage up, Arts teams don’t usually have a lot of it otherwise, so a bit of extra damage push on Castoria’s cards is useful.
Introduction
Berserker
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