Tailtiu

Tailtiu often gets overshadowed in the very heavy blue mage pool, but she has a very interesting unique weapon to make use of. Her Tome of Thoron has an innate wrath effect, making her the only 2-range unit to have wrath. The icing on the cake is it's ability to also grant her darting blow 3 which can help with builds hoping to utilize flashing blade.

This build here is with the wrath effect in mind. The idea is to get Tailtiu into wrath and brazen atk/spd threshold after 1 or 2 rounds of combat. From there, she recharges her special from full at the start of every round, and lull spd/res as well as brazen atk/spd allow her to delete her targets with supercharged glimmers, and at the very least guarantee speed-based follow-ups.

If desired, Swift Sparrow could be placed for the A slot, or flashing blade for her seal. This build is my favorite for the raw destructive power it has.

Her stat fits nice with typical Fury-Desperation set and the Wrath attached to that Thoron will be the icing on the cake; so the concept of this skillset is "Every-turn double with Luna(+10dmg)". If you don't have Time's pulse, just other C skill like Attack wave and then Moonbow can work similarly. Of course Fury 4 is better option if available. I don't recommend Swift sparrow; as she has no merit over other fast mages usually with desperation(like Tharja/Nino) when her HP is over 75%.

Your typical blue tome AoE nuker but it’s not Ophelia.
Tailtiu is the only tome user in the game with the ability to use Wrath, as it is built in her tome. While Ophelia can provide turn 1 specials, Tailtiu is cheaper to get and merge but can be very powerful as well.

! Stats for this build are based on a +ATK fully invested Tailtiu (+10 merged, +10 dragonflowers).

• Preferred Boon: +ATK
• Weapon: Tome of Thoron (+Eff)
• Assist: Reposition
• Special: Blazing Wind
• A skill: Fury 4
• B skill: Special Spiral 3
• C skill: Atk Smoke
• Sacred Seal: Heavy Blade 3

The goal of this build is to charge Tailtiu’s Special in order to spam AoEs like there’s no tomorrow, though you need to blow a hit before being able to fully charge it. While Ophelia can provide Turn 1 AoE hits, once charged Tailtiu can basically do the same and go on and on with her Special.

ATK is the preferred boon as she needs a high offense to land heavy hits. +SPD is not that bad either, though she doesn’t really need extra speed at all. Reposition is there because why not.

A lot of builds prefer to use Brazen skills but I find her to be a bit too squishy to risk lowering her HP enough to activate them - I definitely wouldn’t recommend leaving her in the Enemy zone to take hits. Fury 4 is an expensive yet nice solution as it can lower her health enough to activate the Wrath effect of her tome and also boost her stats from turn one. Fury 3 works the same as well.
Tome of Thoron gives her a nice +6 boost to her speed in Player Phase, meaning she can pretty much double anyone (41 speed + 4 from Fury 4 and an additional +6 from her tome’s Darting Blow effect = 51 SPD).
With the combination of Heavy Blade as a Sacred Seal, Special Spiral and her tome’s Wrath effect you’re guaranteed to land AoE Specials every single turn once charged and nuke everyone.
Atk Smoke is just there to lower her enemies’ offensive power, though anything can work here. Odd/Even Attack Wave is another great choice.
If you want a powerful AoE blue mage but can’t summon Ophelia, she’s the right choice. You can also use Fury 3 instead of 4, making Special Spiral the only expensive skill to fodder.

Not your typical Tailtiu build but she works very nicely and won me every map I used her in (from Infernals to Abyssals). It’s definitely expensive but totally worth it. She’s my unit of choice for all those annoying LHB/GHB I just don’t have time to deal with. She’s my nuker queen.
Team her up with some Wings of Mercy dancers and you’re done. With Fury 4 chipping away her health you don’t need to risk her taking a hit in order to activate your refreshers’ WoM, just let her land some hits and you can go on all day hitting and running away from enemies. Give her some Infantry Pulse help and she’ll destroy everything from turn 1.

Tailtiu is definitely a good investment cause not only she can be an AoE nuker, but can run different builds for pretty much every type of content (Arena, Aether Raids...) while Ophelia is...just there to nuke - and she’s also 5* locked. Tailtiu is more versatile, easier to merge and can also run very dangerous builds. With Fury 4 stats boost, an Astra blessing and double Naga she can even reach 37 DEF, making her definitely less squishy and stronger.

Note: Pretend Mirror Strike 2 is Mirror Impact bc it wasn't in the skill list. Also all credit goes to Akariss here.

Note 2: Run this in an infantry pulse team for maximum effect

So I normally run the "Righteous Thunderclap" build, and it's hecca fun, so this is an aether raids take on it. Mirror impact ensures Tail's survivability by denying the opponent's follow up. Even if they have QR to neutralize it, it becomes a speed check, and with the darting blow refine and her naturally high speed, Tailtiu will still get the double while her opponent can't. This also adds 10 res, which is 8 more damage on her glacies nuke. There are several ways to get her into vantage range, the most common way being lightning traps. Her own allies can even help with this endeavor, such as the inevitable Lif we will get fairly soon. Once she has taken the damage, she is in brazen and wrath range, and because the trap stops the enemy's action, she gets to initiate the fight. I have time's pulse here, but with enough IP support, she can charge glacies without it. If everything is set up properly, she will not disappoint, and her nukes can easily match, or even be stronger than Ophelia's!

This is a build designed to pop specials off as much as possible by using Flashing Blade Astra + Special Spiral which basically turns Astra's cool-down into a permanent 2 cool-down which when combo'd into Flashing Bade can have special activated every turn. Let's say an enemy has more speed than she does, that is why we use Tome of Thoron and (optionally) Reciprocal Aid making the cool-down for Astra at start of turn being from 4 to 1 along with the +10 dmg, the only thing stopping her then is Guard.