Guide
How the kit works
Start with Leihuang Master to place a Thunder Wedge (Skill) and create a Thunder Field around it. The wedge lasts 12 seconds. While the active character is in the field, hitting a target triggers the wedge's Electro Coordinated Attack, at most once every 1.2 seconds.
Unassuming Blade uses Readiness. Yuanwu holds up to 100 and gains 6 per second while the wedge is on the field, even when he is switched out. A wedge Coordinated Attack adds 5. At full Readiness, tapping the Skill uses Thunder Uprising (Skill); holding it consumes the gauge for Rumbling Spark (Forte) and puts Yuanwu in Lightning Infused.
In Lightning Infused, Yuanwu resists interruption and reduces Vibration Strength more efficiently with Basic Attacks, Heavy Attacks and Dodge Counters. Use a Basic Attack within 3 seconds of a Heavy Attack or successful Counterattack to cast Thunderweaver (Forte). Readiness does not regenerate in this state.
Blazing Might deals Electro DMG and gives nearby teammates Lightning Infused for 10 seconds. Both it and Rumbling Spark detonate an existing wedge. When switching out, Lightning Manipulation greatly reduces Vibration Strength around the target.
Reserved Confidence expands the ranges of Thunder Field and Thunder Uprising. It also leaves a wedge when Yuanwu switches out in combat with less than full Readiness. Thunderous Determination increases Thunder Uprising's DMG multiplier by 40% and improves its Vibration Strength reduction.
Build and why
For sets, start with Empyrean Anthem: its two-piece bonus gives 10% Energy Regen. Moonlit Clouds gives the same two-piece bonus. The game also recommends five pieces of Void Thunder; its listed two-piece bonus gives 10% Electro DMG. Rejuvenating Glow is another guide option, though its listed two-piece bonus is 10% Healing Bonus and Yuanwu's listed kit has no healing. The five-piece effects are not supplied here, so compare those in game before choosing.
Abyss Surges is the first weapon choice. It gives 12.8% Energy Regen; a Skill hit grants 10% Basic Attack DMG Bonus for 8 seconds, and a Basic Attack hit grants 10% Resonance Skill DMG Bonus for 8 seconds. Amity Accord instead gives 20% Resonance Liberation DMG Bonus for 15 seconds after the Intro. Stonard gives 18% of that bonus for 15 seconds after casting the Skill.
Verity's Handle is another guide option: it gives 12% Attribute DMG Bonus and, after Liberation, 48% Resonance Liberation DMG Bonus for 8 seconds. Skill casts can extend that effect by 5 seconds each, up to three times. Energy Regen suits Yuanwu if you want his Liberation available more often; Electro DMG supports his attacks.
Leveling priority
A suggested order is Leihuang Master first, since the wedge contributes Coordinated Attacks while Yuanwu is off the field. Follow with Unassuming Blade and Blazing Might, then Leihuangquan and Thunder Bombardment. Adjust the Basic Attack priority if you keep Yuanwu on the field more often.
For maximum ascension you need 170,000 Shell Credit, 4 Crude Ring, 12 Basic Ring, 12 Improved Ring, 4 Tailored Ring, 46 Hidden Thunder Tacet Core and 60 Terraspawn Fungus.
To max all skills, you need 2,030,000 Shell Credit, 25 Crude Ring, 28 Basic Ring, 40 Improved Ring, 57 Tailored Ring, 26 Unending Destruction, 25 Cadence Seed, 28 Cadence Bud, 55 Cadence Leaf and 67 Cadence Blossom.
Resonance Chain nodes worth it
Retributive Knuckles (Sequence 4) is a good team-focused upgrade to consider: casting Blazing Might gives the on-field character a Shield equal to 200% of Yuanwu's DEF for 10 seconds.
Defender of All Realms (Sequence 6) is worth considering for a team that uses DEF. Nearby teammates within the Thunder Wedge (Skill) range gain 32% DEF for 3 seconds. Upholder of Integrity (Sequence 3) adds damage equal to 20% of Yuanwu's DEF when the wedge's Coordinated Attack hits.
For a support-focused build, Steaming Cup of Justice (Sequence 1) and Neighborhood Protector (Sequence 5) are reasonable upgrades to skip if you do not need their damage benefits. The first raises Yuanwu's Basic and Heavy Attack Speed by 20% in Lightning Infused; the fifth gives him 50% Resonance Liberation DMG Bonus while the wedge is present.
Teams
Jinhsi and Verina are listed team options. You can also consider Baizhi, Xiangli Yao or Rover: Spectro. Yuanwu's listed kit does not require a particular teammate element, so choose around the rest of the team's needs rather than forcing an element for his field.
Pair him with an on-field attacker who can hit targets from inside Thunder Field and trigger the wedge's Coordinated Attacks. A healer is a useful third role because Yuanwu has no listed healing. His Liberation gives nearby teammates interruption resistance, while his Outro helps reduce enemy Vibration Strength.
Common mistakes
Do not leave the active attacker outside Thunder Field and expect wedge Coordinated Attacks. Place the wedge where the team can fight around it, and remember that it lasts 12 seconds.
Do not hold the Skill at full Readiness when you mean to use Thunder Uprising (Skill): holding spends the gauge on Rumbling Spark (Forte). Also remember that switching Yuanwu out automatically leaves a wedge only in combat when Readiness is not full.
Do not treat DEF as a damage bonus throughout the base kit. Its stated uses here are in the numbered upgrades, including the Sequence 3 Coordinated Attack damage and Sequence 4 Shield.