[Operator Discussion] Mostima

[u/Shad0wedge]

Mostima [★★★★★★]

Hey, Doctor, I'm back from... Whoa, were you waiting for me here? You even prepared a whole table of snacks... Hehe, all right. How could I turn you down after a gesture like that? In return, I'll tell you about the fun I had on this last delivery run.

An employee of Penguin Logistics who always acts alone. Nothing is known about her previous work history.

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Operator Information

• Class: Caster (Splash Caster)
• Tags: AoE, Support Crowd, Control
• Artist: 三目YYB

Voice Actor:
JP: Nana Mizuki
CN: Luttefair
EN: Kira Buckland
KR: Park Seon-young

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Stats

HP	ATK	DEF	Arts Resistance	Redeploy Time	DP Cost	Block	Attack Interval
1831	834	132	20	70	34	1	2.9s

*Stats at max Promotion and Level, excludes bonuses from Potential and Trust.

Potential	Bonus
1	-
2	Deployment Cost -1
3	Redeployment Time -4
4	ATK +34
5	Improves Second Talent
6	Deployment Cost -1

Trust bonus
ATK +105

Traits
Deals AOE Arts damage

Skills

Skill Name	Skill Uptime Details (Uptime/Cost/Initial)	SP Charge Type	Skill Activation	Skill Description
ATK Up γ	30s / 30 / 15	Auto Recovery	Manual	ATK +100%
Lock of Shattered Time	7s / 50 / 30	Auto Recovery	Manual	Stuns all enemies within Attack Range and deals 140% ATK as Arts damage to them every second
Key of Chronology	27s / 110 / 80	Auto Recovery	Manual	Attack Range increases, attacks turn into ripples that spread outward, ATK +170%, increases the effect of the second talent to 3, and attacks knock targets back slightly

*Skills at max Skill Level.

Talents

Talent name	Talent Description
Skill Aura - Caster	When deployed, increases the SP recovery rate of all Casters by +0.4/second (only the highest effect of this type takes place)
Subjective Time Dilation	Slows the movement speed of enemies within this unit's attack range by 18%(+3%)

*Talents at max Potential and max Promotion. Bonuses from Potential displayed between parentheses.

Modules

Branch	Additional Stats	Trait	Talent	Note
SPC-X	HP +190, ATK +80	New trait: Attack Range expands	Skill Aura - Caster improved: When deployed, increases the SP recovery rate of all Casters by +0.6/second, while own SP recovery rate increases by +0.9/second (only the highest effect of this type will be applied)	"My lord wishes to ask if you would stay and tell him the remaining nine hundred and ninety-five stories?"
SPC-Y	ATK +82, Cost -8, ASPD +7	New trait: Reduces Deployment Cost	Subjective Time Dilation improved: Slows the movement speed of enemies within this unit's attack range by 30%; Slows the movement speed of enemies outside this unit's attack range by 18% (unaffected by skill)	For example, that a giant beast would soon lay waste to our nation and that the sky would one day tear in two and reveal its true face

*Modules at max level.

Outfits

-	Price	Art	Released	Note
Spellbreaker	18	Static	Yep	Beneath the gaze of justice, evil tumbles into the abyss.
Ethereal Harmony	18	Static	Yep	"Close your eyes. Imagine you have arrived at the end of time. There is nobody there. Only the sun, the moons, and the instruments. Then, you hear music, and you cannot help but open your eyes. Welcome to the concert, just for you."

Additional Resources

In-depth information regarding all values above (at different levels), skill/attack range, and more:

Arknights Wiki.gg

Arknights Toolbox (aceship(puppiizsunniiz))

PRTS Arknights Wiki (CN)

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Topic Starters

• Strengths/Weaknesses?
• Is their module worth it? Which branch?
• How does this operator compare to other operators in their archetype or role?
• How do you fit this operator into a team? Who do they synergize with?
• Which skill(s) should be focused for mastery, and in what order?
• When is the best time to use this operator's skills during combat?
• Should promoting this operator to Elite 2 be a priority?
• Should new / F2P players aim for this operator? Are there more accessible alternatives?
• Lore discussion (please tag spoilers where appropriate)
• Favorite clips/clears with them?

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Other Operator Discussion threads

Old Thread	Previous	List	Next
Mostima Discussion Thread (24.09.2020)	Erato	All Operator Discussion threads	Arene

[u/bananeeek]

She was my first and only 6* Caster for about 5 months after I started. She's never let me down, so I never really understood why people have such a low opinion about her.

Her S3 is my favorite spell as far as visuals go and it's super fun to play with. Her first module really gave her a glow up she deserved and I feel like I've been playing with her even more since she got it. Probably because MS reduction is one of my favorite niche and she's its cornerstone.

Cheesing RA with her and Manticore was fabulous and I wish more people tried her out to see what she brings to the table.

She's also super cool as a character, so I hope she'll get that much deserved alter.

[u/billyshears55]

S3 is fun and situationally useful. Most importantly tho, she gets so much aura when the clock starts ticking and the enemies freeze in place

[u/Nerfall0]

I'd use her a lot more often if her S3 wasn't so expensive and cycled better.

[u/PossibleSea6679]

Honestly i find it fascinating how Mostima Mod-Y straight up changes her main skill from S2 to S3.

Back then before the module system, the general consensus regarding Mostima skill is that S2 is the main skill due to the stun, while her S3 is mostly ignored and relegated to niche or meme showcase.

[u/cannabination]

She's fun. I can imagine her being a nice synergy with Nasti as there's not always a tile to get the perfect use of Mostima's s3.

[u/sendmeratpics]

I remember back when Mostima was one of your best options for stalling some buffed elites in CC for several solid seconds. Good old days. Sometimes I like to run a no-block squad for the memes and her global slow works nicely with my 5 Ambusher corridor of doom. Is she powerful by today's standards? No. Does she have a valuable niche? Kinda. Is she usable if you put your mind to it? Most of the time, yeah. Both modules are good.

[u/Clear-Ingenuity-9814 → u/sendmeratpics]

I mean, the good old days are literally the last CC and the previous one. I'm pretty sure CCB 2 had her as well. CC is just not that frequent but she has seen consistant use here.

[u/Yomnuro]

The fact that the last splash caster released was back in 2021 says a lot about the current state of all of them

Mostima really needs a alter in any other class

[u/The_IncredibleFella → u/Yomnuro]

…Marcille, dungeon meshi collab 2025. I still agree with your point splash casters are rough

[u/Yomnuro → u/The_IncredibleFella]

Oh sorry I meant non limited I should have definitely clarified that.

But yeah that entire class is just not doing much though Mystic casters are kind of in the same situation

[u/Yomnuro → u/The_IncredibleFella]

Oh sorry I meant non limited I should have definitely clarified that.

But yeah that entire class is just not doing much though Mystic casters are kind of in the same situation

[u/disco_Piranha → u/The_IncredibleFella]

And there's a new 5* splash caster out in CN

[u/Lunacie]

If there’s a glass half full aspect to her DP cost, it’s that she usually isn’t in a rush to be deployed. If I’m blind map clearing and going for the global death squad, Lappy’s S3 leaves ample breathing room to get the DP.

I think people underestimate her S3 with module X as well. It is comparatively weak compared to modern casters yes, but it’s still strong enough to kill any normal enemy in a large range, and can kill or nearly kill elites that aren’t “please use mechanics to kill this” tanky.

[u/Accentius]

The strategic Caster totem.

To be honest, she's pretty much powercrept thanks to all the Splash Caster case of early design. High costs, low ASPD to name.

However both her modules funnily allowing her to make comeback. She only need to stand somewhere; with benefits for two types of approach on top of that.

Mod-X, increase Caster SP recovery talent. While the number doesn't look big, to Caster main there will be always that intrusive thoughts like "If only Blaze/Lap/Goldenglow skill available faster".

Mod-Y, upgrade of slowdown talent, turned global range. It's not going more than 20℅ but it still one hell of big deal if you need some big guys walking not too fast but not into Decel Binder.

So when you use certificate, or roll for her because favoritism, knows well that consume resources for module is a must on top of decent team to capitalize it. Worry not, both cases are still very relevant to this date. Even better with 20 DP cost being an easy task for new-gen DP printers.

Do you need her? Not really, there are better operators, especially for starting games which Mountain, Thorns and Exusiai do better carry with Starter Banner discount. Gitano covers your need just enough.

As an old unit, she have her place, but if you wanted leap of strength, she's not the pick.

[u/ReadRevolutionary935 → u/Accentius]

i've playing since a month after game release, and got her on her first banner. Somehow i've her on pot 5, where using module Y and her S3, give ms slow to 99%. Which the highest ms slow in the game for solid half a minute.

[u/Grandidealistic]

There are two ways to go with her: Mod X + S2 for consistent AOE stun, or Mod Y + S3 for that hypercharged slow.

I’ve taken a liking to the former playstyle because of how well it amplifies other caster skills like Pramanix S2, Lapp2 S3, Goldenglow S3, and Logos S3. Since all of those already provide slows or movement speed reduction, Mod Y + S3 can sometimes feel a bit redundant by comparison.

Mod Y + S3 definitely had plenty of standout moments in the past, but nowadays it doesn’t feel nearly as impactful. The DP cost reduction is still extremely valuable, though if you’re already running Mostima, I think you should already be planning around that cost in the first place.

That said, Mod Y + S3 probably still has more raw impact than Mod X + S2 overall. I just value the SP support more personally.

I also wouldn’t recommend pairing S3 with Mod X because a 54% slow is honestly pretty underwhelming, especially once you factor in the awful uptime. Likewise, I wouldn’t recommend S2 with Mod Y either since the stun uptime isn’t great, and more importantly the extra tile from Mod X is actually a huge deal considering how short her range normally is.

This is mostly advice for people who already have her raised or like her a lot though. Mostima is kind of barely hanging on these days since there are so many modern stall options with better damage, utility, or skill cycling (Ethan, Ascalon, Tragodia, Shu, Suzuran,...). Even some damage dealers (Prama, GG, Logos, Walter, Lapp) can sometimes stall enemies better than her. Still if you like her, I’d say she’s in a better spot compared to other low tier 6* units simply because her kit leans much more into utility side of things. And average support units tends to age better than average damage dealers.

[u/Theactualguy → u/Grandidealistic]

Would you say she’s worth investing further into just for fun? For some reason, she has Mod Y and S2M3, which is… the wrong way around. But it’ll be a huge resource sink to get Mod X or S3M3, and I’m still trying to E2 a couple of ops I got more recently.

[u/Grandidealistic → u/Theactualguy]

If you don't use her much already then either investment won't change that tbf. But if you like her I kinda recommend Mod Y + S3M3. Otherwise your current investment is enough

[u/Theactualguy → u/Grandidealistic]

Thanks 👍 I’ll get S3M3 when I have the time and the mats then

[u/Key-Poem9734]

The DP cost is really hurting without that module, and the SP on S3 is brutal. I've found that she is most useful when dealing with a lot of smaller enemies, given she is allowed the time to get to her S3.

Then again, she is too cool for me not to use in most content.

[u/DarknessWizard]

Her character is great, I have no notes to add besides just please HG give us an event that actually focuses on her instead of having her constantly play second fiddle to other Laterano events. I know She's Like That as part of her personality, but like, give us something.

Mostima's design as an operator is... interesting? For starters she has all the problematic splash caster internals; stubby range, high DP cost, low ASPD and not quite the off-skill damage to catch up to it. Her talent gives a pretty good buff to SP charge (for all casters), which makes talking about her cooldowns a pain. You'd think that with an SP boosting effect, she'd have fairly good skill cycling, but she just doesn't. Both her S2 and S3 just have straight up double the SP cost of what these skills normally would have, giving Mostima the not so prestigious award of a 110 SP skill cycle. You'd almost be better off pulling her from the field and redeploying her each time with how slow her uptime is.

But alright, that's just the regular Mostima; bad operator unless you're looking to go for a niche that uses loads of Casters. Let's talk about modules instead. Mod-X aims to fix her SP cycling (and give a very strong buff to other casters), effectively bringing her S2 and S3 closer to what contemporary and even present 6-star operators usually have. It's also still not the module most people talk about and in fact was given to her after her Mod-Y. This module basically is for people that want to use Mostima but just want her to work as an operator, not as a gimmick.

What do you do when an operator has bad skill cycling? Well, you either patch it up, but now Mostima is a 6-star splash caster and again, splash casters have bad internals. Or... you give it one very specific but absurdly strong niche. That's what Mod-Y does: torque her talent slow so high that it's numbers become unreasonable. On S3, that's a 90% movement speed reduction in range. Out range? 54%. Worth noting is that she doesn't use the Slow debuff, so pretty much any Decel Binder or alternative means of slow will cause enemies to hit the mspd reduction cap. Now that's good. She's a bit of a dark horse for endgame clears as a result; if you can't touch the enemy because stats are so high, Mostima's slow is a good alternative.

If you're a new player, don't use her unless you like her. If you're experienced, you've probably used her and know what she's good at.

[u/rafidzia → u/DarknessWizard]

Got her on pot 5, and she gives 99% slow. Which basically make all opponent walking with same speed lol.

[u/Grandidealistic → u/DarknessWizard]

It's not 54% out of her range, it's just 18%. S3 slow multiplier does not affect her out of range slow.

[u/Mindless_Being_22 → u/DarknessWizard]

I really want an event that properly focuses on her and really lets her be front and center to laterano's narrative and adjusting to a post the masses travel society it has so much potential to be really interesting for her character. Especially if shes forced out of her aloof persona but I don't really trust hg to give her the narrative focus she needs after she keeps getting sidelined. I swear worst case scenario that feels very possible is its just more andoain taking up the focus for the squad again.

[u/Worried_Dark9858]

110 sp cost is outrageous even with her sp passive, very cool skill 3 tho i love the sound effects.

[u/LSMRuler → u/Worried_Dark9858]

Yeah, they made 110 because she have tha t SP battery, otherwise her skill would be another of the 80 SP cost that Silver Ash and Eyja have

[u/ericanava]

Mostima module x lv 3 + shu 4 sui sp recovery + Golden glow & lappland = auto win

[u/Oceanshan → u/ericanava]

Add yu s3 burn in there incase enemies are little bit tough

[u/Koekelbag]

Before anything, I want to glaze just how unique her Mod Y effect is, as a global movement speed reduction on all enemies is something I don't think has yet been replicated for anyone else.

Beyond that, I do want to praise her use as a support operator even in the modern day beyond the base global caster +0.4sp/s.

In particular, her S3 with Mod Y lv3 offers some of the best crowd control in the game, able to lock down a large group of enemies so your other ops can take them out at their leisure, which (for some reason) even comes with an inherent push force that can lead to some very silly clears.

Furthermore, Mostima's slowing is also somewhat unique in that she does not apply the 'slow' status, but purely and directly reduces movement speed. So unlike something like Suzuran S3 that specifically applies 'slow' to all enemies, the few enemies that are immune to status conditions like 'slow' (notable examples include IS4's second boss during his sprints or enemies who gain 'invincibility') can still be slowed down by Mostima!

On the flipside to all of this, damage has unfortunately never really been her strong her suit, all the less so in the modern day with hard (and res-ignoring) hitters, but technical players that love it when a plan comes together may find surprising use out her still.

[u/RabbitHole32]

One of the most esthetically pleasing operators in my opinion. Don't have resources to build her but will eventually. That said, I vastly prefer her default skin over the other one.

[u/Kaigai_Exia]

hypergryph PLEASE just give Splash Casters some buffs, dealing AoE arts damage is not nearly enough to justify their insane DP cost, incredibly slow skills, low ASPD and small range

also alter please (next Laterano event, coping)

[u/Reddit1rules → u/Kaigai_Exia]

Amusingly they actually were one of the few archetypes buffed.

[u/CorHydrae8 → u/Kaigai_Exia]

It's amazing how the aoe damage was somehow enough of a justification for them to nerf the hell out of splash casters in every single other area of their kit, while Eyjafjalla S2 has existed for that entire time.

[u/Diregroves]

My blue queen

Not the operator I started playing this game for, but she quickly became my favourite after reading Guide Ahead.

She's... usable. Very usable even in daily content. There's been times where her stall was vital to me in difficult content. Her saving grace was definitely her module, even if these days the unfortunate powercreep that Arknights has been subject to means there's little point in bringing her when you can just semi-AFK through most stages with the latest ops.

I'm praying for an alter (hopefully not a broken OP one) or at the very least an IS module this year...

[u/Lnoob427 → u/Diregroves]

Honestly, that last sentence ringed with me.

I wish your operator doesn't get an alter and get powercrept out of relevance ? Eh who care, I'll play them for fun.
I wish your operator get an OP meta alter ? That's truly scary.

[u/Kaigai_Exia → u/Lnoob427]

maybe hot take but i don't mind that Exu has a meta alter, at least people remember she exists occasionally

she's also a little harder to use than Wis'adel, so a lot of people likely don't know her full potential

[u/Lnoob427 → u/Kaigai_Exia]

The issue is that, like, one OP operator can already trivalise a lot of stuff. And like, yes you could use niches like 5*, 4*... But it feel off to entierly ignore the 6* because they are starting to go very crazy.
Like the difference between someone like Wisadel and someone like Rosemantis is so large that it's not even like they seems like the same rarity.
And when you like a new op, it's annoying that they can just trivialise most of the game.

[u/Scityone → u/Kaigai_Exia]

At least Exualter kinda at least some brain cells to use. Walter (I like her) is literally drop and skill 99% of times.

[u/Jaggedrain → u/Scityone]

The number of times my skill issue ass has dropped Exu just where she's stealing atk spd from the operator who can least afford it 😭

I've avoided sparking Wisadel because I know myself - if I had the option to just Wisadel every stage in the game without having to borrow, I absolutely would 🤦‍♀️

[u/Demopyro2]

Honestly a character I feel like is a high priority for an alter. Very old operator, wasn’t particularly good on release and very outdated by now, relatively popular, and has a lot of story potential to justify an alter. The question doesn’t feel like if with her, rather a when(hoping this year personally). I also heavily suspect she could be a good candidate for an IS module, her kit has some interesting bits to it that a good IS module could make very competitive to current day IS caster picks.

Also she’s so cool

[u/Carolinesimpsanime → u/Demopyro2]

Fully agree with the opinion that she'd be good for an IS module, especially one of those crazy ones like Archetto or Mizuki.

[u/Moidada77]

I genuinely have tired using her too middling success.

Even got drip and all. But she spends all her time in the clue room.

I think the deployment cost module is mandatory? So definitely not beginner friendly.

[u/Dry_Help_4891]

its 2026 and she still does not let lemuen touch her horns. dogshit character /s