Guide
How the kit works
Before a fight, use The Glorious Mysteries when you can. The first ability Sunday uses on an ally in the next battle gives that target 50% more DMG for 2 turns.
Use Ode to Caress and Cicatrix on the ally you want to support when it is available. It restores Energy equal to 20% of their maximum, with a minimum of 40, and makes the target and their summon The Beatified. They gain CRIT DMG equal to 30% of Sunday’s CRIT DMG plus 12%. The effect lasts 3 turns, with its duration decreasing at the start of Sunday’s turns. It applies only to the most recent target, excluding Sunday, and ends if he is knocked down.
Follow with Benison of Paper and Rites on that ally. It lets the character and their summon act immediately and raises their DMG by 30% for 2 turns. A target with a summon gets an extra 50% DMG boost. The Sorrowing Body also gives the Skill’s target 20% CRIT Rate for 3 turns. Skill removes one debuff from the target and refunds 1 Skill Point when used on The Beatified.
The immediate action does not trigger on Harmony characters. Use Gleaming Admonition when you need a basic attack: it deals Imaginary DMG equal to 100% of Sunday’s ATK to one enemy.
Build and why
Use four pieces of Sacerdos' Relived Ordeal. Its two-piece effect gives Sunday 6% SPD. The four-piece effect gives the ally targeted by his Skill or Ultimate 18% CRIT DMG for 2 turns, stacking twice. Both abilities fit the condition.
For the planar set, Broken Keel is a good choice if you can reach 30% Effect RES: it gives the team 10% CRIT DMG and provides 10% Effect RES itself. Lushaka, the Sunken Seas gives Sunday 5% Energy Regeneration Rate and gives the first character in the lineup 12% ATK if Sunday is not in that slot. Put the ally you want to receive that ATK in the first slot.
Choose CRIT DMG on the body, SPD on the feet and Energy Regeneration Rate on the rope. Use HP Percentage or DEF Percentage on the sphere. For substats, look for CRIT DMG first, then SPD and Effect RES. CRIT DMG strengthens the Ultimate’s buff; SPD helps Sunday take turns to use his Skill.
A Grounded Ascent is the first weapon choice. After Sunday uses Skill or Ultimate on one ally, it restores 6 Energy and gives the target a Hymn stack, up to three. Each stack gives 15% DMG for 3 turns. Every two such ability uses also recover 1 Skill Point.
But the Battle Isn't Over is next, with Energy Regeneration Rate and occasional Skill Point recovery. Earthly Escapade gives Sunday CRIT DMG and can give teammates CRIT Rate and CRIT DMG through Mask. For a 4-star option, Past and Future increases the DMG of the next ally to act after Sunday uses Skill.
Leveling priority
Follow the game’s order: level Ode to Caress and Cicatrix first, then Benison of Paper and Rites, The Sorrowing Body and Gleaming Admonition. The Ultimate and Skill are the main ways Sunday supports his chosen ally. The Talent improves the CRIT Rate support attached to Skill, while Basic is last because his build focuses on helping teammates.
To ascend Sunday fully, you need 308,000 Credit, 65 Chordal Mirage, and 15 each of Tatters of Thought, Fragments of Impression and Shards of Desires.
For all skills at maximum, the separate cost is 3,000,000 Credit, 8 Tracks of Destiny, 18 Firmament Note, 69 Celestial Section, 139 Heavenly Melody, 12 Lost Echo of the Shared Wish, 41 Tatters of Thought, 56 Fragments of Impression and 58 Shards of Desires.
Eidolons worth it
As a suggested order, look at Millennium's Quietus first. After Sunday uses Skill, the target ignores 16% of enemy DEF when dealing DMG and their summon ignores 40% for 2 turns. It adds a benefit to the ability you already want to use on your main target.
Faith Outstrips Frailty is another option: the first Ultimate recovers 2 Skill Points, and The Beatified deal 30% more DMG. At the far end, Dawn of Sidereal Cacophony lets the Talent’s CRIT Rate boost stack up to three times, extends its duration by 1 turn and applies it through Ultimate. When that boost takes effect, each 1% CRIT Rate above 100% becomes 2% CRIT DMG.
Sculpture's Preamble restores 8 Energy at the start of Sunday’s turn. If you prefer new effects over ability levels, you can leave E3 and E5 for later: they raise skill levels rather than adding a separate effect.
Teams
A team to try is Jing Yuan with Sunday, Ruan Mei and Gallagher. Sunday focuses his buffs on Jing Yuan, Ruan Mei is another Harmony buffer, and Gallagher provides sustain. Sunday’s support is not restricted to Imaginary allies, so the team can mix combat types.
Phainon and Yunli are also named teammate options if you want to support a character without relying on the summon-specific bonus. Bronya or Sparkle can be considered for another support slot, but do not expect Sunday’s Skill to make a Harmony character act immediately.
Common mistakes
Do not keep switching the Ultimate target without a reason. Only the most recent eligible target keeps The Beatified, and using Skill on that target is what refunds a Skill Point.
Do not ignore turn order. If your damage dealer acts before Sunday, his Skill can give that ally another immediate action afterward. Check the order when adjusting SPD, and remember that the immediate action does not work on Harmony targets.
Do not build Sunday around his Basic damage instead of his support. Give him CRIT DMG for the Ultimate and use an Energy Regeneration Rate rope. If you choose Broken Keel, check that his Effect RES actually reaches 30%; if you choose Lushaka, check the lineup order.
