Guide
How the kit works
Core Passive: Thief of Flames gives Promeia two Trial by Cold when she enters the battlefield. Her attacks generate Corrosive Chill, though some moves are exceptions. At 50 Corrosive Chill she converts 50 into one Trial by Cold, up to two. Freeze, Disorder, Vortex and an Abloom that hits an enemy also grant Corrosive Chill.
With enough Energy, use EX Special Attack: Execution - Glacial Death (Special) to throw the cape and gain Absolute Order. With her Additional Ability active, an EX Special Attack hit also applies Presumption of Guilt. During Bound Absolution, use Special Attack: Execution - Descending Frost, then keep holding after landing to spend Trial by Cold on EX Special Attack: Execution - Merciless Judgment (Special). Its finisher triggers Abloom at 635% Attribute Anomaly DMG against an eligible affected enemy.
An attack shortly after Glacial Death automatically leads to EX Special Attack: Execution - Shrouded in Shadow (Special). After a Perfect Dodge, you can also use it for 40 Energy. Follow it with Special Attack: Execution - Layered Frost, then hold after landing for Merciless Judgment. The cape state can automatically trigger a Perfect Dodge once every 20 seconds.
Chain Attack: Hanging Judgment and Ultimate: Glaciating Impalement trigger Abloom at 100% and 250% respectively when their heavy attack hits an eligible affected enemy. The supported Anomalies are Ice, Ether, Electric, Fire, Physical and Wind. Ultimate also grants Frost Oath, which can be consumed after Ultimate, Chain Attack or Merciless Judgment to follow up with Layered Frost.
Build and why
Use four pieces of Notes From the Chained with two pieces of Phaethon's Melody. Notes From the Chained gives Ice DMG and grants 48 Anomaly Proficiency for 30 seconds when Promeia triggers Abloom. Her Freeze also raises her All-Attribute Anomaly DMG and Disorder DMG by 16% for 30 seconds. Phaethon's Melody adds 8% Anomaly Mastery.
For the main stats, pick Anomaly Proficiency on disc 4, Ice DMG Bonus on disc 5 and Anomaly Mastery on disc 6. Look for Anomaly Proficiency first in substats, then Percent ATK. Initial Anomaly Mastery above 150 also increases Promeia's Anomaly Proficiency and the squad's Abloom DMG through her Core Passive.
Frostfall Sickle is the first weapon choice. Her Special Attack and EX Special Attack build its Ice DMG stacks, with 35% more Abloom DMG at two stacks. Fusion Compiler is next: it gives ATK and builds Anomaly Proficiency stacks through those attacks. Electro-Lip Gloss is another option against enemies affected by Attribute Anomaly. For a two-piece alternative, consider Freedom Blues for Anomaly Proficiency.
Leveling priority
Follow the game's order: Core Passive first, then Special Attack, Chain Attack, Basic Attack, Assist and Dodge. The passive supports the resource cycle and Abloom, while Special Attack includes the finisher you spend Trial by Cold on. Chain Attack also triggers Abloom; Basic Attack helps you reach its follow-ups.
For maximum ascension, prepare 800,000 Denny, 4 Basic Anomaly Certification Seal, 32 Advanced Anomaly Certification Seal and 30 Controller Certification Seal.
For all skills, the listed materials are 2,905,000 Denny, 25 Basic Freeze Chip, 75 Advanced Freeze Chip, 250 Specialized Freeze Chip, 5 Hamster Cage Pass, 9 Marrow-Draining Thorn and 60 Higher Dimensional Data: Toxic Edge.
Mindscapes worth it
Faltering Conviction is a good upgrade to consider for damage. It gives 40 Anomaly Proficiency and increases the multiplier of Abloom triggered by consuming Trial by Cold by 120%.
Innocent Idealism gives one Trial by Cold after Ultimate if the resource is below its maximum. It also makes the squad's Abloom ignore an extra 20% DEF against targets with Presumption of Guilt.
To Be Continued adds a special Abloom at a fixed 200% multiplier when Promeia consumes Trial by Cold to trigger Abloom. It also restores 5 Corrosive Chill and 100 Decibels, at most once every 15 seconds. Promeia's Attribute Anomaly DMG and Disorder DMG also ignore 15% of enemies' All-Attribute RES.
If you stop after M2, the later upgrades are reasonable to leave out. Cruel Moonlight and The Dying Moth raise skill levels, while Ruthless Accusation restores Corrosive Chill when Promeia triggers Abloom. They remain steps on the way to M6 rather than upgrades you can select individually.
Teams
Vivian and Yuzuha are teammates to consider alongside Promeia. Vivian is an Ether Anomaly character, while Yuzuha is a Physical Support character. Either satisfies the condition for Promeia's Additional Ability, so the two can also be used together with her.
With that ability active, using an EX Special Attack gives Promeia 30% Ice Anomaly Buildup Rate for 30 seconds. Frostbite applied by any squad member lasts three seconds longer, and the squad's Abloom ignores 40% DEF on a target with Presumption of Guilt.
Velina is another Anomaly option, this time with Wind. Nangong Yu is an Ether Stun option, but pair her with an Anomaly or Support teammate as well if you want Promeia's Additional Ability active.
Common mistakes
Don't spend a finisher without checking the target. EX Special Attack: Execution - Merciless Judgment (Special) still deals Ice DMG, but its Abloom needs the finishing hit to land on an enemy affected by one of the listed Anomalies. It also consumes Trial by Cold when activated.
Don't assume every cape hit builds Corrosive Chill. Bound Absolution and Basic Attack: Whirling Blade do not accumulate it on hit, and Merciless Judgment does not either. Use the other parts of the kit and the squad's reactions to refill the resource.
Don't forget the follow-ups. Several moves can go straight into the fifth hit of Basic Attack: Sweeping Edge, which can lead back into Merciless Judgment if you have enough Trial by Cold. During Bound Absolution, remember that the automatic Perfect Dodge has a 20-second cooldown.