Guide
How the kit works
Start attacking with Basic Attack: Full Firepower. Repeatedly press or hold it to enter Crouching Shot and extend the attack. Move during Crouching Shot to use Rolling Shot, or release the input to fire a Finishing Shot at enemies in front. Moving ends the Steady Shot bonus, so weigh the lost damage against the safer position.
Use Special Attack: Stand Still for up to three piercing attacks in a line. With enough Energy, EX Special Attack: Clearance Time (Special) fires a stronger piercing attack and makes Billy invulnerable during the skill.
Dodge: Risky Business provides an invulnerable dash. After a Perfect Dodge, use Dodge Counter: Fair Fight to attack enemies in front while invulnerable. Dash Attack: Starlight Sanction hits a large area if you move during the dodge, or a line if you do not.
When a Chain Attack is triggered, select Billy for Chain Attack: Starlight Mirage. If another squad member shares his Attribute or Faction, Additional Ability: Team Starlight gives his next Ultimate 50% more damage per Chain Attack, up to two stacks. At maximum Decibel Rating, use Ultimate: Starlight, Shine Bright; activating it resets the stacks.
When the active character is launched, Quick Assist: Power of Teamwork brings Billy in with an attack. Evasive Assist: Flash Spin dodges an incoming attack and activates Vital View; follow it with Assist Follow-Up: Fatal Shot for a large frontal attack. Billy is invulnerable during all three.
Build and why
Woodpecker Electro is a strong four-piece choice. Its two-piece bonus gives 8% CRIT Rate, and critical hits with a Basic Attack, Dodge Counter or EX Special Attack each grant 9% ATK for 6 seconds. The three durations are tracked separately, so Billy has several ways to gain the bonus.
Shadow Harmony is another option if you use Dash Attacks often. Its two-piece bonus raises their damage by 15%, while its four-piece effect grants up to three stacks of 4% ATK and 4% CRIT Rate when the qualifying attack hits. Dawn's Bloom instead boosts Basic Attack damage, with another 20% increase for an Attack character after an EX Special Attack or Ultimate.
The game recommends four pieces of Fanged Metal with two pieces of Woodpecker Electro. Fanged Metal gives 10% Physical DMG and, after a squad member inflicts Assault, 35% more damage against that target for 12 seconds.
For disc 4, choose CRIT Rate or CRIT DMG; for disc 5, choose Physical DMG Bonus or Percent ATK; use Percent ATK on disc 6. The listed substat priority is Percent ATK, then CRIT Rate, then CRIT DMG.
The Brimstone builds ATK stacks from Basic Attacks, Dash Attacks and Dodge Counters, all moves Billy can use regularly. Cloudcleave Radiance ignores 20% Physical RES; its extra damage and CRIT DMG require the equipper to activate an Ether Veil. Heartstring Nocturne gives 50% CRIT DMG, though its Fire RES ignore does not directly benefit Billy's Physical attacks. Starlight Engine Replica is another option: hit from at least 6 meters with a Basic Attack or Dash Attack for 36% more Physical DMG against that target for 8 seconds.
Leveling priority
Follow the game's order: Core Passive: Steady Shot first, then Basic Attack: Full Firepower, Chain Attack: Starlight Mirage, Special Attack: Stand Still, Dodge: Risky Business and finally Quick Assist: Power of Teamwork. The passive and Basic Attack support the damage Billy deals during Crouching Shot; the later upgrades improve attacks you use around it.
For maximum ascension, you need 800,000 Denny, 4 Basic Attack Certification Seal, 32 Advanced Attack Certification Seal and 30 Pioneer's Certification Seal. Maxing all skills takes 2,905,000 Denny, 25 Basic Physical Chip, 75 Advanced Physical Chip, 250 Specialized Physical Chip, 5 Hamster Cage Pass, 9 Ferocious Grip and 60 Higher Dimensional Data: Ethereal Pursuit.
Mindscapes worth it
Roaming Gunslinger is worth considering for its defensive change: Rolling Shots become dodges, grant invulnerability and can trigger Perfect Dodges. A Perfect Dodge made this way automatically follows with a Dodge Counter, whose damage also increases by 25%. Moving still ends the Steady Shot bonus.
Starlight Hero is a useful later upgrade. Ten hits or a Perfect Dodge grant 6% damage, stacking up to five times; getting knocked back or launched resets it. Dazzling Entrance is a smaller early improvement, giving 2.7 Energy when a Dash Attack or Dodge Counter hits, once every 5 seconds.
Teams
Billy wants teammates who can support his field time and create opportunities for Chain Attacks. A teammate with the same Attribute or Faction activates Additional Ability: Team Starlight, letting Billy build damage for his next Ultimate through Chain Attacks.
Common mistakes
Do not move during Crouching Shot without a reason and expect Core Passive: Steady Shot to remain active. Rolling Shot can help you reposition, but movement ends the bonus. A knockback, launch or return to standby ends it too.
Do not use Ultimate before checking whether you have built the available Chain Attack stacks, especially when Additional Ability: Team Starlight is active. You can stack its bonus twice, but any Ultimate activation resets it.
Do not build around a weapon or set condition you cannot meet. Starlight Engine Replica needs a hit from at least 6 meters, while Cloudcleave Radiance's extra bonuses require an Ether Veil activation. For Fanged Metal's four-piece effect, someone in the squad must inflict Assault on the target.
