Guide
How the kit works
Start with Overture of Departure, then use Towards the Daybreak. The Intro lets you continue at Basic Attack Stage 3 and gives 15 seconds of Starlume Acceleration. Using Overdrive during that window restores an extra Resonance Rate point. Overdrive also switches Aemeath into her Mech.
Use attacks and Shared Voyage to change forms and build Synchronization Rate. After Basic Attack Stage 4, you have five seconds to use Seraphic Duet (forte) if you have at least 100 Synchronization Rate. It spends 100 points, switches forms and restores one Resonance Rate. Overdrive strengthens the next two uses; the first within 30 seconds does not consume Trail stacks.
At four Resonance Rate during Unbound, Instant Response makes Charged II faster. Use it to restore 200 Synchronization Rate, then cast Heavenfall Edict: Finale (liberation) when both resources are full. Finale spends them and returns Aemeath to her own form.
Build and why
Use five pieces of Trailblazing Star. Its two-piece effect gives 10% Fusion DMG; the supplied data does not describe its five-piece effect. Flaming Clawprint and Molten Rift are alternatives with the same two-piece Fusion bonus.
Everbright Polestar is the first weapon choice. It gives 12% All-Attribute DMG Bonus, and inflicting Tune Rupture - Shifting or Fusion Burst lets Aemeath's Resonance Liberation DMG ignore 32% DEF and 10% Fusion RES for eight seconds. That fits attacks counted as Resonance Liberation DMG.
Emerald of Genesis offers Energy Regen and ATK after casting Resonance Skill. Feather Edge is a 4-star option with ATK and Resonance Liberation DMG Bonus after Liberation. For stats, consider Crit. Rate, Crit. DMG, ATK and Fusion DMG; Energy Regen is also worth considering for access to Liberation.
Leveling priority
A suggested leveling order is To Sculpt the Silence, Towards the Daybreak, Infinity Calibration, Shared Voyage, then Overture of Departure. The Forte includes her enhanced form-switching attacks, while Liberation covers Overdrive and Finale.
For maximum ascension, collect 170,000 Shell Credit, 4 LF Exoswarm Core, 12 MF Exoswarm Core, 12 HF Exoswarm Core, 4 FF Exoswarm Core, 46 Our Choice and 60 Moss Amber.
To raise all skills to the maximum, you need 2,030,000 Shell Credit, 25 LF Exoswarm Core, 28 MF Exoswarm Core, 40 HF Exoswarm Core, 57 FF Exoswarm Core, 26 Gold in Memory, 25 Broken Wing Polarizer, 28 Monowing Polarizer, 55 Polywing Polarizer and 67 Layered Wing Polarizer.
Resonance Chain nodes worth it
For damage upgrades, consider A Zephyr-Kissed Journey to You (sequence 6), followed by Fervor Sightly Burns Bright as New (sequence 3) and Downy Notes of Snowfluff (sequence 2). This is a suggested priority rather than a ranking supported by the supplied guides.
Sequence 6 makes targets take 40% more Resonance Liberation DMG from Aemeath and lets the relevant mode's damage critically hit at fixed values. It also doubles Trail stacks inflicted through her Forte. Sequence 3 increases Finale's multiplier by 100% and changes how Between the Stars gains its bonuses.
Sequence 2 strengthens Seraphic Duet (forte). Gilded Glimmer of the First Dawn (sequence 1) improves Heavy Attacks in Instant Response, while Ethereal Waltz on Binary Tides (sequence 4) gives the team an attribute damage bonus. Voyage to the Astral Shore (sequence 5) includes a revival effect. You can leave these as optional goals; none is required for her base rotation.
Teams
Pick teammates around Aemeath's mode. In Tune Rupture, team responses to Tune Rupture - Interfered add Rupturous Trail. In Fusion Burst, team members inflicting Fusion Burst add Fusion Trail. Those stacks strengthen Seraphic Duet (forte).
Between the Stars also rewards contributions from different Resonators: three in Tune Rupture mode or two in Fusion Burst mode give Aemeath the full Crit. DMG bonus and 25% Finale DMG Amplification. Consider a sustain teammate who can contribute to the chosen mode.
Guides name Lynae and Mornye as teammates, with Denia and Chisa also suggested. Check their kits against the mode you want to use. Silent Protection gives other teammates 10% All-DMG Amplification for 20 seconds, increased to 20% for those who inflict the effect specified by that mode.
Common mistakes
Don't use Resonance Skill after Stage 4 without checking Synchronization Rate. Seraphic Duet (forte) needs at least 100 points and its five-second window is easy to miss. Build the resource with attacks and form switches first.
Don't cast Finale as soon as it appears in the rotation plan. Heavenfall Edict: Finale (liberation) requires Unbound and both resources at their limits. At full Resonance Rate, a Charged II during Instant Response and Unbound fills Synchronization Rate.
Don't assume every Fusion set has the same full-set effect, or that the five-piece effect of Trailblazing Star is described here. In team building, don't ignore the mode's stack conditions: a teammate needs to contribute the relevant effect for the larger Outro bonus and the passive stacks.