Guide
How the kit works
Start with Anticipator when you can. On entering battle it hits a random enemy, has a 100% base chance to apply the Skill's Bleed and gives Luka one Fighting Will stack. He starts battle with another stack, so he can have enough for his enhanced attack immediately.
Use Lacerating Fist on the target you want to focus. It deals 120% of Luka's ATK as Physical DMG and has a 100% base chance to apply Bleed for three turns. At the start of the enemy's turn, that Bleed deals 24% of its Max HP, capped at 338% of Luka's ATK. Once the relevant passive is unlocked, the Skill also removes one buff from the target.
Flying Sparks gives Luka a Fighting Will stack after Direct Punch or the Skill, up to four stacks. At two or more stacks, Direct Punch becomes Sky-Shatter Fist. The enhanced attack consumes two stacks and ends with an uppercut. If that hit lands on a Bleeding enemy, its Bleed immediately deals 85% of its original damage.
Use Coup de Grâce against the priority target. It gives two Fighting Will stacks, has a 100% base chance to increase the target's DMG received by 20% for three turns, then deals 330% of Luka's ATK as Physical DMG. With another passive unlocked, each Fighting Will stack obtained also restores 3 Energy.
Build and why
Use four pieces of Prisoner in Deep Confinement. It gives 12% ATK and lets Luka ignore 6% of the target's DEF for each DoT on it, up to three DoTs. Champion of Streetwise Boxing is an alternative: it gives Physical DMG and builds ATK when Luka attacks or is hit.
For the planar set, Revelry by the Sea gives 12% ATK and increases DoT DMG by 12% at 2400 ATK or 24% at 3600 ATK. Space Sealing Station is another option if you want ATK; it gives an extra 12% when Luka reaches 120 SPD.
The game's build uses ATK Percentage on the body and rope, SPD on the feet and Physical DMG Boost on the sphere. Its substat order is ATK Percentage, SPD, Break Effect, CRIT Rate and CRIT DMG. ATK helps Luka's damage and raises the cap on his Skill's Bleed.
Good Night and Sleep Well is the first Light Cone choice: it increases Luka's damage for each debuff on the target, up to three, and also affects DoT. In the Name of the World increases damage against debuffed enemies and boosts Effect Hit Rate and ATK when he uses his Skill. Those Many Springs is another option, with Effect Hit Rate and a chance to make targets receive more damage.
Leveling priority
Follow the game's order: level Lacerating Fist first for its hit and Bleed. Next is Coup de Grâce, followed by Flying Sparks, which handles the extra Bleed damage. Level Direct Punch last.
For full ascension, you need 246,400 Credit, 50 Broken Teeth of Iron Wolf, 12 Ancient Part, 13 Ancient Spindle and 12 Ancient Engine.
To raise all skills to their maximum, you need another 2,400,000 Credit, 5 Tracks of Destiny, 12 Obsidian of Dread, 54 Obsidian of Desolation, 105 Obsidian of Obsession, 12 Regret of Infinite Ochema, 28 Ancient Part, 42 Ancient Spindle and 42 Ancient Engine.
Eidolons worth it
As a suggested progression target, A Champion's Applause adds another Bleed damage trigger after the enhanced attack's uppercut hits a Bleeding target. It deals 8% of the original Bleed damage for each Direct Punch hit already made during that attack. The three initial hits count, and the unlocked passive can add more.
The Enemy is Weak, I am Strong is worth considering when you fight enemies with Physical Weakness: the Skill then gives an extra Fighting Will stack. Never Turning Back gives 5% ATK for each stack obtained, up to four times.
Fighting Endlessly is useful against Bleeding targets, while Born for the Ring and The Spirit of Wildfire raise skill levels. You do not need to target those nodes on their own, although earlier Eidolons are required to reach later ones.
Teams
Luka fits a team that wants DoT and a target debuff. Kafka is a Lightning DoT teammate to consider; Sampo is a Wind option with DoT and debuff roles. Extra DoTs also help Luka use more of the DEF-ignore effect from Prisoner in Deep Confinement.
Silver Wolf is a Quantum debuffer you can consider alongside him. For a Break-focused team, Fugue brings a Fire Break role, while Boothill is a Physical Break attacker. Natasha is a Physical sustain option if the team needs help staying alive.
Luka gives these teams his own Bleed and a damage-received increase from his Ultimate. Keep his single-target focus in mind when choosing the rest of the lineup.
Common mistakes
Do not spend the enhanced Basic ATK on a target without Bleed if you want the immediate extra Bleed damage. The Technique hits a random enemy, so check which target received the effect before choosing your attack.
A 100% base chance is not a guarantee. Check that Bleed landed instead of assuming it did. Also watch Fighting Will: Luka can hold four stacks, while his Ultimate gives two, so using it near the cap can waste stacks.
Do not assume the Skill's Bleed always deals 24% of a target's Max HP. Its damage is capped by Luka's ATK. If you use a planar set with a stat threshold, check that Luka actually reaches it.
