BEST SI BUILD IN ARKNIGHTS ENDFIELD

Si’s best build in Arknights Endfield is a 3-piece Type 50 Yinglung set (the Soft Armor and two Beacons) with the Eternal Xiranite Channeling Gloves in the hand slot. All four are Version 1.6 pieces with Intellect, Strength and a Combo Skill DMG line, and Jade Vessel is her best weapon.

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In our Si damage calculator, this build’s Ink Lung hits about 29% harder than the best Eternal Xiranite build. Eternal Xiranite is still the right set in a team where nobody else wears it, and two Ultimate Gain builds trade her damage for more Amp windows.

How we ranked these builds. Every number comes from our own data: piece stats from the game’s equipment table, and damage from the Si damage calculator at Level 90, Skill Rank 12, talents maxed, Potential 0, Jade Vessel at weapon substat and skill rank 9, an Ink Lung that consumes 4 Infliction stacks, 3 stacks of Yinglung’s Edge, her Ultimate’s Amp off, no enemy DEF, and crit-weighted expected damage. The table ranks Si’s own damage. The team value of her Amp and of Eternal Xiranite is explained below but not scored. The weapon and potential notes also cite post-launch community rotation testing of whole-team damage. Checked October 17, 2026, on Version 1.6.

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TL;DR - Key Points

• Best set: Type 50 Yinglung Soft Armor, two Type 50 Yinglung Beacons, and Eternal Xiranite Channeling Gloves.
• Stats: Intellect, then Strength, with Combo Skill DMG as the third line on every piece.
• Support swap: Eternal Xiranite (MOD Armor, Channeling Gloves, two Rangefinders), only when no teammate already holds the set. Its team buff does not stack.
• Amp uptime: the Eternal Xiranite Ultimate Gain pieces or AIC Fieldwork bring her Ultimate back faster, at the cost of more than half her Ink Lung damage.
• Weapon: Jade Vessel, then Khravengger, then Long Heritage on her own damage.
• Cost: 360 Wuling Stock Bills and 50 Pyrrolite Components per piece, four crafts in total.

Why Type 50 Yinglung

Si’s biggest hit is her combo skill. Fully Envisioned fires when a teammate consumes or absorbs Cryo or Heat Infliction, and its Ink Lung deals 750% ATK plus 100% for each stack consumed, up to 4 stacks. Her Ultimate’s Giant Ink Lung is 500%. The combo is on a 15 second cooldown, so Combo Skill DMG is the line that moves her damage most.

Type 50 Yinglung is built for exactly that:

• Bonus stat: ATK +15%.
• Set effect: whenever any operator on the team casts a battle skill, the wearer gains a stack of Yinglung’s Edge, worth DMG +20% on the wearer’s next combo skill. It stacks 3 times, so a full set of stacks adds +60% to the Ink Lung.

Three team battle skills between Ink Lungs fill it. With only one stack, the build is still about 17% ahead of Eternal Xiranite on the Ink Lung (313,247 against 268,556).

Version 1.6 added the first Intellect and Strength pieces with Combo Skill DMG lines, which is what makes the set work on her:

Piece	Slot	Stats
Type 50 Yinglung Soft Armor	Armor	Intellect 87, Strength 58, Combo Skill DMG +20.7%
Eternal Xiranite Channeling Gloves	Gloves	Intellect 65, Strength 43, Combo Skill DMG +34.5%
Type 50 Yinglung Beacon (x2)	Kit	Intellect 32, Strength 21, Combo Skill DMG +41.4%

Why the gloves come from another set. Every set bonus in Endfield needs 3 pieces, and there is no 2-piece tier, so the fourth slot is a free stat stick. Type 50 Yinglung has no Intellect and Strength gloves in our data, so the Soft Armor and both Beacons hold the set and the Channeling Gloves take the hand slot. The 1.6 client also ships a second item named Type 50 Yinglung Gloves, but its stats are not in our data yet. We will revisit this build once they are.

A second Beacon beats a Knife. The Type 50 Yinglung Knife T1 (Intellect, Strength, All Skill DMG +27.6%) in the last Kit slot raises her Ultimate by about 19% but costs about 3% on the Ink Lung. The Ink Lung comes around far more often, so the second Beacon wins.

Si Gear Builds Compared

Si’s own damage per hit with each build, Amp off, 3 Yinglung’s Edge stacks:

Build	Ink Lung	Giant Ink Lung (Ultimate)	Ultimate Gain
Type 50 Yinglung: Soft Armor, Channeling Gloves, 2 Beacons	346,990	52,571	0%
Type 50 Yinglung: Soft Armor, Channeling Gloves, Beacon, Knife T1	335,349	62,693	0%
Eternal Xiranite: MOD Armor, Channeling Gloves, 2 Rangefinders	268,556	47,636	0%
Eternal Xiranite: MOD Armor, Channeling Gloves, Rangefinder, LYNX Slab	264,252	53,134	0%
Tide Surge: Tide Fall Light Armor, Deepsink Gloves, Turbid Cutting Torch, Eternal Xiranite Power Core	218,506	72,176	37%
AIC Fieldwork: Plate, Hands, Ember, Eternal Xiranite Power Core	171,496	52,195	84%
Eternal Xiranite: Overalls, Gloves, 2 Power Cores	163,070	47,636	82%
Pre-1.6 Eternal Xiranite: Armor, Gloves T1, Power Core T1, Hanging River O2 Tube	159,842	48,912	21%

With her Ultimate’s 36% Cryo Amp up, every row rises by the same factor, so the order does not change. The last row is the Eternal Xiranite build this site listed before the 1.6 pieces reached our gear data: Will pieces she cannot use and a Treatment Bonus Kit, at less than half the Ink Lung damage of the Type 50 Yinglung build.

All five builds we list for her, with their pieces, are on the gear sets by operator page.

When to Use Eternal Xiranite Instead

Eternal Xiranite’s set effect: after the wearer applies Amp, Protected, Susceptibility or Weakened, the other teammates gain DMG Dealt +16% for 15 seconds. Si’s Ultimate, No One Spoils the Fun, gives the whole team Cryo Amp and Heat Amp, so every cast triggers it.

The catch is that the buff cannot stack. Xaihi, Ardelia, Arcane and Gilberta all run Eternal Xiranite as their usual build, and if one of them is on the team, Si’s copy adds nothing. That covers most of her Cryo teams, which is why Type 50 Yinglung is the default.

Switch to Eternal Xiranite when nobody else holds it, for example a Heat team of Laevatain, Wulfgard and Akekuri:

• Armor: Eternal Xiranite MOD Armor (Intellect 87, Strength 58, Combo Skill DMG +20.7%)
• Gloves: Eternal Xiranite Channeling Gloves
• Kit: two Eternal Xiranite Rangefinders (Intellect 32, Strength 21, Combo Skill DMG +41.4%)

Her Ink Lung drops about 23% against the Type 50 Yinglung build, and in exchange the other three operators get DMG Dealt +16% after each of her Ultimates. A LYNX Slab in place of the second Rangefinder trades a little Ink Lung damage for a bigger Ultimate and comes out even.

Amp Uptime Builds

Her Ultimate costs 80 energy, each Ink Lung returns 10, and every cast is a 12 second window of up to 36% Cryo and Heat Amp for the team. Through her talent Proxy’s Patronage, it also cuts up to 20 seconds off the combo cooldown of the operator in Team Position 1. Two builds stack Ultimate Gain Efficiency for more of those windows:

• Eternal Xiranite, Ultimate Gain line: Overalls, Gloves and two Power Cores, +82% Ultimate Gain with Intellect and Strength on every piece, and the team buff when nobody else holds the set.
• AIC Fieldwork: Plate, Hands, Ember and an Eternal Xiranite Power Core. The set adds Ultimate Gain +10% and DMG Dealt +20%, for +84% Ultimate Gain and slightly more Ink Lung damage than the Eternal Xiranite version. This is the pick when a teammate already holds Eternal Xiranite.

Both cost more than half of her Ink Lung damage. Use them when the team leans on her Amp, or on the cooldown cut for a slot 1 carry, more than on her own hits.

Stat Priority

1. Intellect, her main attribute.
2. Strength, her secondary attribute. Every piece in the builds above rolls both.
3. Combo Skill DMG, the third line on every piece of the main build.
4. Ultimate Gain Efficiency, only for the Amp uptime builds.

The Artificing Planner finds the cheapest fodder for raising each of these lines on the 1.6 pieces.

Best Weapons for Si

With the recommended gear, her own damage per hit at weapon substat rank 9:

Weapon	Ink Lung, skill rank 1	Ink Lung, skill rank 9	Why
Jade Vessel	225,070	346,990	ATK up to +44.8%, next combo DMG up to +70% after her Ultimate, and DMG Taken up to +21% on the target she Immobilizes, for the whole team
Khravengger	211,189	265,807	Cryo DMG lines off her battle skill and combo, but its Strength line is only her secondary attribute
Long Heritage	179,070	199,478	Free from the 1.6 Protocol Pass. Main attribute and Cryo DMG lines, plus a team Arts DMG line the calculator leaves off

Long Heritage’s team line grants Arts DMG when the wielder gives another operator Arts Amp. Whether her Cryo and Heat Amp count is not confirmed, so that line is excluded above. If it does count, it narrows the gap for the team as a whole.

Post-launch rotation testing of whole-team damage puts the gap smaller than the per-hit table: Jade Vessel came out about 10% ahead of a fully ranked Long Heritage, and Khravengger roughly matched Long Heritage even without its secondary effect, which a rotation built around it could use. If you own none of the three, Exemplar is the fallback.

Si Potentials

What each potential does, from her potential table:

Potential	Effect	Worth it?
P1	Artful Intent stores 20% of the damage taken instead of 13%	A solid damage gain, more so on single targets
P2	After her combo, ATK +8% plus 3% per stack consumed, for 10 seconds	A solid damage gain
P3	Ultimate damage and its Cryo and Heat Amp x1.2 (36% to 43.2%)	Small for total team damage
P4	Ultimate costs 15% less energy (80 to 68)	Does not change the gear: Ultimate Gain pieces are still not worth it in the main build
P5	Combo DMG x1.15, cooldown 2 seconds shorter (15 to 13), and counts one extra stack	The big one. It gains a lot even in a standard rotation, before any rotation built around the shorter cooldown

The ratings follow post-launch community rotation testing of whole-team damage. If you are pulling copies, P1 and P2 are good stops and P5 is the real spike.

Crafting Cost

Every 1.6 piece in these builds is a Pyrrolite-only recipe at 360 Wuling Stock Bills and 50 Pyrrolite Components. The Type 50 Yinglung build is four crafts (the Beacon twice), for 1,440 Stock Bills and 200 Pyrrolite Components. The Eternal Xiranite support build costs the same, with the Rangefinder crafted twice.

If you are building both, craft the Channeling Gloves first: they sit in both builds.

Teams

Which build she wears depends on who else is on the team, mostly on whether someone already holds Eternal Xiranite. Our Si best teams guide covers the six teams worth building around her and the Team Position 1 rule. In post-launch testing, Si with Last Rite, a Will-build Arcane and Xaihi deals the most team damage, just ahead of Si as the main damage dealer with Tangtang, Arcane and Xaihi. For level-by-level gear and weapon steps, see the Si progression guide.