Qiubai is an operator who's been receiving a lot of negativity lately, in no small part due to FOMO on upcoming strong operators, especially the true limited Kirin R Yato. But her kit happens to be right up my alley (and I like her character quite a lot too), so hopefully this guide can help balancing things out by showing her on her own merits.
Basic Information
Qiubai is a 6* Lord Guard, placing her in a branch that's been historically well-regarded, but hasn't gotten a new high rarity member in ~2.5 years. She has a few different things that help her carve out her own spot: she's among the best ground-based Arts units, she has access to crowd control, she has overall stronger attacks off skill, and she has more than one useful skill.
Offensive Stats
Qiubai has average Attack, a 1.3 second attack interval, below-average dps, and standard Lord range. As with all Lords her range is great, but it's up to her talents and skills to make up for her lacking stats.
Defensive Stats
Qiubai has slightly below-average HP, above-average Defense, 10 Res, and 2 block. While she's no tank, her high Defense is nice for dealing with trash mobs.
Cost and Trust
Qiubai has a below-average 20 DP cost, and her trust is split evenly between Attack and Defense. HG seems fixated on the notion that Lords should be at least partially defensive, resulting in some of the 6*s' trust being diverted to Defense. Her DP cost is quite nice, however, being low enough that you can often open maps with her.
Trait: Can perform ranged attacks that have an 80% Attack multiplier
"Ranged Attack" is any basic attack against something Qiubai isn't blocking, and can hit flying enemies. Because the Attack penalty is applied before Defense it worsens her ability to deal with anything that has a meaningful Defense stat.
First talent: Find an Opening
0.1s after attacking an enemy affected by Slow or Bind, deal an additional hit of Arts damage equal to 40% of Attack (unaffected by trait).
"Slow" refers specifically to the debuff called "Slow" rather than any kind of movement speed reduction. Talent 1 can trigger off of any instance of damage with Qiubai as the source, with the exception of talent 1 itself.
This talent provides a nice chunk of extra damage when it applies, especially since it's not reduced by her trait. Something to keep in mind is that in Arknights debuffs are applied before damage by default, so any of Qiubai's attacks that inflict Slow/Bind will trigger this talent. Both s1 and s2 can guarantee Bind/Slow on their own, while s3 and basic attacks rely on talent 2 for Bind. And this is a bigger damage boost than it might appear; Lords in general suffer from low dph on their basic attacks, especially at range, and this being Arts damage lets Qiubai circumvent that.
Second talent: Falling Petals
Attacks have a 20% chance to Bind the target for 1.5s
Talent 2 can trigger off of any instance of damage with Qiubai as the source, with the exception of talent 1.
20% is an aggravatingly low chance, but the payoff is high; not only will the Bind proc talent 1 on the current attack, but the duration is just long enough for the next attack to benefit as well. While you generally can't rely on this Bind for the purposes of cc, it still makes her basic attacks markedly better compared to most Lords in the long run.
Incidentally, Bind immunity is effectively nonexistent; there have been two CC Risks that made certain units Bind immune, and other than that nothing else to the best of my knowledge.
Modules
While Lords do not have modules yet on CN as of the time of writing, I want to call attention to the fact that Qiubai stands to profit greatly from hers. Both of her talents are important to her kit and would benefit from simple numeric improvements, so unless HG decides to staple on new effects instead her upgrades are near certain to be valuable. The base Attack improvement will also be significant, as she has high talent/skill multipliers to make up for the lower base stats from being a Lord.
First skill: Halting Feather
At m3{m0} Halting Feather has 0 initial SP, costs 4{5} SP, recovers SP by attacking, lasts for a single attack, and is automatically activated. It causes the affected attack to ignore Qiubai's trait and inflict Bind for 3{2.5} seconds. When the 3{2.5} seconds are over or the target dies, the target and all enemies within a 1.7 tile radius take Arts damage equal to 300%{240%} of Qiubai's Attack. The Bind ends prior to the AoE damage and thus doesn't guarantee a talent 1 proc on the primary target, but talent 2 can still trigger off of the AoE damage or an external source can apply Bind/Slow to cause talent 1 to proc.
S1 is an odd skill; the first thing that likely stands out is that it provides a 3s bind but costs only 4 SP; accounting for the cast time it can give ~46% Bind uptime on its own, and with external ASPD buffs and/or SP batteries it's possible to permaBind a single target. Outside of that, it's got one of the biggest splash radii in the game, it's running off of Lord range, and it's Arts. In particular, the splash AoE can reach outside of her range, expanding her possible reach even further beyond the vast majority of melee units. While s1's damage isn't exceptional, it's still solid and enough to do its job, especially since there aren't any exact replacements for its unique features.
Second skill: Holding Shadow
At m3{m0} Holding Shadow has 5{4} initial SP, costs 10{12} SP, recovers SP by attacking, lasts 5 seconds, and is manually activated. Upon casting the skill Qiubai's range changes to a 1x4 line straight ahead of her, and she deals Arts damage equal to 300%{240%} of her Attack (unaffected by trait) to all ground enemies in range and Slows them for 1.2s. For as long as the skill lasts all enemies within range are Slowed and Qiubai gains +140%{+90%} Attack (she still attacks normally during the duration, and it lasts long enough for her to perform 4 basic attacks if no ASPD modifiers are applied), and after 4.88 seconds (the +Attack and Slow are still active) she deals physical damage equal to 300%{240%} of her Attack (unaffected by trait) to all ground enemies in range.
S2 is a deceptively good skill; the ingame description leaves the details of various interactions unmentioned, and as a result the skill can look unimpressive if you don't sit down and study the various related mechanics. But in practice almost all of those inner workings are in s2's favor: the starting attack applies Slow and debuffs apply before damage so the starting attack benefits from talent 1 (along with the remainder of the skill), she has just enough time to squeeze in a 4th normal attack even though duration might not seem long enough, and the ending attack occurs before the +Attack and Slow expire (although the associated talent 1 procs occur after the +Attack expires).
In short, s2 deals considerably more damage than you might think; the AoE portion alone will wipe out trash mobs and soften up elites, which the single target portion can finish off. The Slow is quite useful as well; the Slow debuff inflicts -80% move speed so enemies in her range will be nearly frozen in place for the duration of the skill. Offensive recovery may be off-putting, but the Lord chassis does well with it thanks to the extra range giving more attack uptime and the weaker basic attacks letting her farm more SP off of trash mobs, and 10 SP is still rather cheap. The change in range, however, is generally a downgrade; while the 1 extra tile in front lets her reach things that melee units other than Fortresses can't, it comes at the cost of the 4 tiles to her sides that can allow her to cover multiple lanes easily.
Third skill: Questioning Snow
At m3{m0} Questioning Snow has 45{38} initial SP, costs 55{58} SP, recovers SP over time, lasts 30 seconds, and is manually activated. While s3 is active, her range expands, she gains +55%{+40%} Attack, her attacks deal Arts damage, she attacks up to 3 targets at once, {talent 1's Attack scale is multiplied by 2}, ranged attacks are no longer penalized by her trait, and every attack she makes gives her +13 ASPD for the remainder of the skill, up to 8{6} stacks.
That's a long list of effects, but the short version is that s3 does a lot of damage. The ASPD boost goes hand-in-hand with her second talent, giving it more chances to proc, and also lets her proc talent 1 more times within the 1.5s bind duration. S3 also offers good cc once she's ramped up (which happens quickly). As a rule of thumb, once she's ramped up talent 2 will proc often enough that talent 1 will proc for ~50% of her attacks*, and an external source of 100% Bind/Slow uptime is worth ~29% more dps (plus it eliminates RNG from the equation, and any incidental Bind/Slow during downtime still buffs her basic attacks). The skill is also hindered by its rotation, which is a little long by modern AK's standards, though not prohibitively so. I do want to emphasize, however, that even standalone s3 has more than enough damage for just about anything short of bosses (or extremely high Res elites, but then why are you using an Arts skill?); external Bind/Slow are more of a luxury pick for when you'd be bringing an enabler anyway, letting you double dip on cc and dps increases rather than picking one or the other. Also, don't forget that s3 is multitarget; it will incidentally wipe out mobs without getting distracted from bigger targets.
- The math behind this number: during s3 her ASPD is fast enough that a talent 2 proc lasts long enough for her to make 3 attacks. This means that, for any given attack, if talent 2 procs on that attack, the previous attack, or the one before the previous attack, talent 1 will proc on the current attack. The probability of an event with a 20% success rate occurring at least once out of 3 trials is 1-(1-0.2)^3=0.488, which is roughly 50%.
Mastery Choices
S3 is Qiubai's "meta" skill from her appearances in stuff like high risk CC, but that doesn't mean you should necessarily focus on it. AK is oversaturated with this sort of Big Damage skill, from the venerable SA and Eyja1 to the newfangled Mlynar, so if you have some of those skills already Qiubai's own s3 may not have as much to offer. One of the big things that sets it apart is that it's much more receptive to buffs than most of its competitors--other Big Damage skills typically have large +% Attack which dilutes external Attack buffs, but Qiubai s3 focuses more on ascale and ASPD which multiply external Attack buffs, on top of her getting dps boosts from external Slow/Bind. Qiubai can reach astronomical total damage numbers in situations where you're stacking enablers...the problem being that that level of firepower is rarely warranted.
But even so, s3 is still a good skill in a vacuum (without external Slow/Bind), and it also has extremely valuable masteries due to gaining the new talent 1 multiplier from them. And the Bind, while not perfectly consistent, offers something that other Big Damage skills don't have that is more widely relevant: crowd control, which can keep elites and bosses safely away from your squishier units. If you don't already have a glut of Big Damage skills to choose from, want to take advantage of s3's characteristics, and/or just want to use Qiubai for your Big Damage needs then don't hesitate to master and use it.
S2, on the other hand, is where I suggest most people start. While the Big Damage niche is hotly contested, Qiubai s2 is so far ahead of other fast rotation AoE damage skills that its competitors might as well not exist. The only ones that are remotely close are Fiammetta s2 (if sweetspotted, and Fia is a ranged unit) and Ch'en1 s2 (which is outdamaged by the AoE portion of Qiubai s2 alone even with max mod, and has a higher SP cost).
As for s1, it's hard for me to give it a fair evaluation; its something I wouldn't recommend most players master due to the cost and s2/s3 being overall more valuable, but if you plan to m9 Qiubai anyway you'll find it surprisingly useful. An advantage I didn't mention above is that unlike s2 it doesn't change her range, allowing her to cover multiple lanes more easily.
Usage
I feel like Qiubai is a very straightforward unit, so there's little to say here; the confusion with her skills is more numerical than functional. The biggest tip I can give is that when using s2 you should place her according to s2's range rather than her base range; she'll only be able to hit those side tiles with her weaker basic attacks, so their value is very limited.
Synergies
This section won't be as brief as the above; Qiubai's kit offers a lot of options in this area. Something I haven't fully discussed yet is that Qiubai in general has high compatibility with enablers, since both her talent 1 and all her skills have good modifiers.
Suzuran
Suzuran's s3 pairs perfectly with Qiubai s3, providing not only 100% Slow uptime but also 40% Fragile, for an overall 80% dps increase alongside even more cc. And their rotations line up perfectly; Suzu's s3 lasts 5s longer than Qiubai's, while her cooldown is 5s shorter accounting for her own SP battery. Given that Qiubai already has good damage on her own, however, this synergy tends to work in reverse from what most people think--Qiubai doesn't benefit from having Suzuran inasmuch as Suzuran benefits from Qiubai. Suzuran's duration, Slow, healing, range, and ease of use all give her utility over other enablers like Gnosis, Warfarin, and Aak--at the cost of a lower damage increase. But when paired with Qiubai who turns Slow into dps, Suzuran can have her cake and eat it too.
Ines
Ines' first talent will apply a 5s Bind the first time she hits any given enemy, allowing Qiubai 4 guaranteed talent 1 procs (assuming Qiubai isn't distracted by any other enemies, and that Qiubai's s3 isn't active) which substantially improves her damage output and circumvents RNG. Ines' range aligns perfectly if you put her directly in front of Qiubai, plus she negates Stealth and applies a move speed penalty to let Qiubai take even more advantage of her range. And taking advantage of this combo has little opportunity cost, as Ines will likely be on your squad by default if you own her due to how good she is.
Swire2
Swire2 s2 is an alternative Slower who's more focused on personal dps (which she has a lot of), but she has incredible uptime; factoring in her s2's ability to store charges and plant mines it's realistic for her to provide Qiubai with near 100% Slow uptime for both skills and basic attacks, making Qiubai's downtime performance much better. Swire2 s2's range is perfect for being placed directly in front of Qiubai, and thanks to her base stats and passive revive she also acts as the tank/healer of the combo.
Ethan/Earthspirit
These two are the budget alternatives if you want Bind/Slow. Ethan's duration matches Qiubai s3 exactly, but he has some RNG of his own (heavily weighted in your favor with his module) and he doesn't offer much Bind during downtime. Earthspirit (max module required) has 5s less duration than Qiubai s3, but in exchange her Slow will have 100% uptime during s2, and a very respectable ~80% uptime during her downtime that significantly improves Qiubai's basic attacks and mostly makes up for her slightly shorter skill duration.
Liskarm
Lord range is perfect for getting charged by Liskarm, letting Qiubai use her s2 more often (or s3 if you're so inclined). Liskarm also has her own RNG AoE Stun via s2, which won't trigger Qiubai's talent but still adds to the overall cc of the pair.
Skadi2
Qiubai in general has good scaling with buffs, so she can obviously benefit greatly from Skadi2 s2's passive Attack buff. A less obvious benefit is that since Qiubai already has above-average Defense Skadi2 can bring her up to ~DPS Defender level, making Qiubai surprisingly durable.
Ch'en1
With her X3 module, Ch'en1 is a premier SP battery for offensive (and defensive) recovery skills, improving Qiubai s1's Bind uptime, but most importantly letting her use s2 more often. Ch'en1's s2 is essentially a weaker Qiubai s2, but you can use the two of them together for more damage, alternate between them for more coverage, or use one of Ch'en1's other skills instead.
Stainless
Stainless can help Qiubai in different ways, depending on her skills. Stainless s2 is a strong but focused SP battery, perfect for improving Qiubai s1's Bind uptime. Stainless s3 provides a permanent target for her offensive recovery s2, and can help compensate for the lost range. And since Qiubai's s3 attacks 3 targets very quickly its one of the best options for making the most of Stainless s3's dps, though this is normally overkill.
Base Skills
At e0 Qiubai's base skill is Guard Expert α, a Training Room skill. Guard Expert α provides +30% training speed for Guards.
At e2 Guard Expert α upgrades to Combat Techniques: Lord. Combat Techniques: Lord provides +45% training speed for Guards, and an additional +30% for Lords.
The branch-specific kind of Training Room skill ultimately can't measure up to Irene and the m#-specific kind, so Qiubai's base skill is functionally irrelevant for the most part. Adding insult to injury, she can't train herself and she's just about the only Lord where you'd consider mastering multiple skills.
Closing
This guide is more to raise awareness than instruct, but I'll still try to answer any questions on the subject. The subject of my next guide is uncertain, due to the current schedule shuffling, but I can at least promise a Muelsyse guide when the time comes.
In case you'd like to see Qiubai in action for yourself, here are some videos (possible spoilers ahead). These are generally showing her performance in extreme scenarios and at max level, but they should give you an idea of what her upper limit is like. There are many fewer videos than normal this time as well, in this case due to me not having enough time to look for good ones.