Guide
How the kit works
Before combat, use At Ocean's Abode to create a moving dimension for 20 seconds. Enemies inside follow it without attacking allies. Starting combat against them gives each enemy two DoT states, with a 100% base chance. Only one allied Dimension Effect can exist at a time.
The Gladius of Conquest deploys a three-turn Zone at the start of combat and recovers one Skill Point. Use Overtone Hum: Chorus After Dark Tides to hit all enemies and increase their damage taken by 20% for three turns, with a 100% base chance.
When an ally attacks, Sirenic Serenade has a 100% base chance to inflict Wind Shear, Bleed, Burn or Shock, prioritizing a different state. These last two turns and deal DoT at the start of each turn. Bleed scales with the enemy's Max HP, but is capped by Hysilens's ATK.
Use Maelstrom Rhapsody to deploy the Zone again and damage all enemies. The Zone reduces their ATK by 15% and DEF by 25%. For each instance of DoT an enemy takes inside it, Hysilens deals Physical DoT equal to 80% of her ATK. This can trigger at the start of each turn or after an ally attack, up to eight times, and cannot repeatedly trigger itself.
The Bubble of Banquets makes DoTs already on an enemy deal 150% of their original damage immediately when Hysilens uses her Ultimate. The Zone lasts three turns, counting down at the start of her turns, and disappears if she is knocked down. Use Aeolian Mode: Echoes in Still Waters for a single-target hit when you want to save a Skill Point.
Build and why
Use four pieces of Prisoner in Deep Confinement. The two-piece bonus gives 12% ATK, and the four-piece bonus ignores 6% DEF for each DoT on the target, up to three. Hysilens can apply different DoT states herself. For the planar set, use Revelry by the Sea: it gives 12% ATK and increases DoT damage by 12% at 2400 ATK or 24% at 3600 ATK.
Champion of Streetwise Boxing is a relic alternative with Physical DMG and stacking ATK. Space Sealing Station is a planar alternative: it gives 12% ATK, plus another 12% at 120 SPD.
For main stats, choose Effect Hit Rate or ATK Percentage on the body, SPD or ATK Percentage on the feet, Physical DMG Boost on the sphere, and Energy Regeneration Rate or ATK Percentage on the rope. Prioritize Effect Hit Rate, SPD, then ATK Percentage in substats. The Fiddle of Pearls increases Hysilens's damage for Effect Hit Rate above 60%, reaching its 90% cap at 120%.
Why Does the Ocean Sing is the first weapon choice. It gives 40% Effect Hit Rate and can inflict Enthrallment, increasing the target's DoT received based on Hysilens's debuffs. Reforged Remembrance is an alternative with Effect Hit Rate and stacks that add ATK and let DoT ignore DEF. Those Many Springs gives 60% Effect Hit Rate and can inflict Unarmored to increase damage received. For a four-star option, Eyes of the Prey gives Effect Hit Rate and DoT damage.
Leveling priority
Follow the game's order: level Maelstrom Rhapsody first for the Zone and its damage, then Overtone Hum: Chorus After Dark Tides for its team-wide damage-taken effect. Level Sirenic Serenade next for its DoT states, and leave Aeolian Mode: Echoes in Still Waters until last.
For maximum ascension, you need 308,000 Credit, 65 Invasive Clot, 15 Fear-Stomped Flesh, 15 Courage-Torn Chest and 15 Glory-Aspersed Torso.
For all skills, you need 3,000,000 Credit, 8 Tracks of Destiny, 18 Fiery Spirit, 69 Starfire Essence, 139 Heaven Incinerator, 12 Daythunder Anamnesis, 41 Fear-Stomped Flesh, 56 Courage-Torn Chest and 58 Glory-Aspersed Torso.
Eidolons worth it
You Ask Why Hearts Cry is the standout upgrade. Ally DoT becomes 116% of its original value, and Hysilens can inflict an extra Talent DoT state that can coexist with states already present.
Tell Me Why Waves Roar High is a good next option: while the Zone is active, the damage boost from The Fiddle of Pearls applies to all allies. Lo, How Time Flows By is another option for team damage because the Zone reduces all enemies' All-Type RES by 20%.
When to Return From Where You Lie raises the Zone's Physical DoT trigger limit to 12 and increases its damage multiplier by 20%. You can stop at E1 if you do not want further upgrades. The level increases at E3 and E5 are less distinctive effects, though you must pass them to reach later Eidolons.
Teams
Kafka is a strong partner to consider because she brings Lightning DoT. Black Swan adds a Wind DoT role, giving Hysilens's Zone more DoT damage to work with. Sampo or Serval are other listed DoT options.
For the remaining slots, consider a buffer such as Ruan Mei and a sustain character such as Huohuo. Gallagher or Dan Heng • Permansor Terrae are other sustain options. Hysilens helps the whole team through increased enemy damage taken and the Zone's DEF reduction, so her contribution is not limited to her own damage.
You do not need teammates of a particular element for Hysilens to apply her Talent states: she can inflict Wind Shear, Bleed, Burn and Shock herself when allies attack.
Common mistakes
Do not treat a 100% base chance as a guaranteed application. Build Effect Hit Rate for Hysilens's debuffs and her damage boost, rather than relying on ATK alone.
Do not forget that the opening Zone has a three-turn duration and disappears if Hysilens is knocked down. Keep her alive and watch its remaining duration before using the Ultimate.
Using the Ultimate while enemies have no DoTs misses the immediate damage from The Bubble of Banquets. Let allies attack and apply states first when the situation allows, but remember that the Ultimate also deploys the Zone and recovers a Skill Point.
