Introduction: how Acheron works
Acheron is a Lightning DPS from The Nihilithy. As is common from characters of this path, she works based on debuffing the enemy. Acheron doesn’t have Energy for her Ultimate like the other characters, instead, her Ultimate bar has nine charges, that are filled with points of Slashed Dream. Each time Acheron uses her skill or an enemy is debuffed in her presence, the enemy receives a stack of Crimson Knot and Acheron receives a point of Slashed Dream. If an ally debuffs multiple enemies, the enemy with the most Crimson Knots will receive the stack. When Slashed Dream reaches 9 points, the Ultimate can be activated. During the Ultimate, the enemies’ Toughness is reduced, regardless of Weakness Types, as well as All-Type RES by 20%, lasting until the end of the Ultimate. The Ultimate consumes all the Crimson Knot stacks to deal Lightning damage, however, if an enemy is killed with Crimson Knot stacks remaining, the Knots will be transferred to the next enemy with the most stacks. It’s a lot of text, but in practice, it’s really simple.
One thing really interesting about Acheron is her Technique: she one-shots every enemy besides bosses. This on places like MOC doesn’t matter, but it speeds up Simulated Universe and Overworld exploration. Now even if Acheron doesn’t one-shot the enemy, she still deals Lightning DMG equal to 200% of Acheron’s ATK to all enemies, reduces the Toughness of all enemies irrespective of Weakness Types, and after using the Ultimate, she gains 1 point of Slashed Dream and inflicts 1 stack of Crimson Knot on a single random enemy. In my opinion, this is one of the most complete Techniques in the game.
Relics
I would like to start this section by pointing out that, unfortunately, I don’t have access to Honkai: Star Rail’s test servers, so I can’t provide detailed numbers by myself. For that purpose, I will be using numbers from Prydwen Institute to base my argument.
Stats
For stats on your relic pieces, you will want:
Body: CRIT Rate/CRIT DMG
Feet: ATK%/Speed (Depends on your build)
Relic Sets
Acheron being a debuffer DPS character makes her benefit the most from Pioneer Diver of Dead Waters Relic Set:
| Pioneer Diver of Dead Waters |
|---|
 |
| 2-Piece Effect | Increases DMG dealt to enemies with debuff by 12%. |
| 4-Piece Effect | Increases CRIT Rate by 4%. The wearer deals 8%/12% increased CRIT DMG to enemies with at least 2/3 debuffs. After the wearer inflicts a debuff on enemy targets, the aforementioned effects increase by 100%, lasting for 1 turn(s). |
This is the best relic set if you can keep the 3 debuffs active at all times, which is a must with Acheron anyway, so I don’t see any reason to not use this. Other options are:
| Band of Sizzling Thunder |
|---|
 |
| 2-Piece Effect | Increases Lightning DMG by 10%. |
| 4-Piece Effect | When the wearer uses their Skill, increases the wearer’s ATK by 20% for 1 turn(s). |
Increases her lightning damage and increases ATK after using the skill, which is common on Acheron.
| Musketeer of Wild Wheat |
|---|
 |
| 2-Piece Effect | ATK increases by 10%. |
| 4-Piece Effect | The wearer’s SPD increases by 6% and Basic ATK DMG increases by 10%. |
Increases ATK and SPD which is good, but Acheron doesn’t gain anything from using her basic attack. I would only use this as a last-case scenario.
Planar Ornaments
Stats
For the stats on your Planar Ornament, you will want:
Planar Sphere: ATK%
Link Rope: ATK%
Planar Ornament sets
As I’m going to mention later, Acheron has a Trace that increases her DMG based on how many Nihility characters are on the team besides her up to 2 characters. That being the case, she benefits the most from Izumo Gensei and Takama Divine Realm Planar Ornament:
| Izumo Gensei and Takama Divine Realm |
|---|
 |
| Increases the wearer’s ATK by 12%. When entering battle, if at least one other ally follows the same Path as the wearer, then the wearer’s CRIT Rate increases by 12%. |
This increases her ATK and CRIT Rate, which is good for any DPS character, and Acheron is always going to need at least one Nihility character by her side, even with eidolons. Other options are:
| Space Sealing Station |
|---|
 |
| Increases the wearer’s ATK by 12%. When the wearer’s SPD reaches 120 or higher, the wearer’s ATK increases by an extra 12%. |
ATK increase based on SPD. Usually, it’s good to have high speed on your characters
| Inert Salsotto |
|---|
 |
| Increases the wearer’s CRIT Rate by 8%. When the wearer’s current CRIT Rate reaches 50% or higher, the wearer’s Ultimate and follow-up attack DMG increases by 15%. |
You will need to build Acheron’s CRIT Rate anyway, and most of her damage comes from the Ultimate.
Substats
For Substats, the overall priority is: SPD > CRIT Rate = CRIT DMG > ATK%
Light Cones
As with every 5 stars in the game, Acheron’s best Light Cone is Along the Passing Shore, her signature Light Cone:
| Along the Passing Shore (The Nihility) |
|---|
 |
| Increases the wearer’s CRIT DMG by 36/42/48/54/60%. When the wearer hits an enemy target, inflicts Mirage Fizzle on the enemy, lasting for 1 turn. Each time the wearer attacks, this effect can only trigger 1 time on each target. The wearer deals 24/28/32/36/40% increased DMG to targets afflicted with Mirage Fizzle, and the DMG dealt by the wearer’s Ultimate additionally increases by 24/28/32/36/40%. |
This Light Cone gives a significant boost, as it gives everything Acheron needs: CRIT DMG, increased damage, another debuff/affliction, and Ultimate DMG. One thing that makes a huge difference is that with this Cone, Acheron now gets two stacks of Shattered Dream per use of her skill, as she is now also applying Mirage Fizzle. This speeds up her game loop, making reaching the Ultimate faster.
| Incessant Rain (The Nihility) |
|---|
 |
| Increases the wearer’s Effect Hit Rate by 24/28/32/36/40%. When the wearer deals DMG to an enemy that currently has 3 or more debuffs, increases the wearer’s CRIT Rate by 12/14/16/18/20%. After the wearer uses their Basic ATK, Skill, or Ultimate, there is a 100% base chance to implant Aether Code on a random hit target that does not yet have it. Targets with Aether Code receive 12/14/16/18/20% increased DMG for 1 turn. |
Assumes debuffs at all times. The second best option for Acheron. It also applies a debuff, Aether Code, which allows Acheron to gain 2 stacks of Shattered Dream. However, this Light Cone provides significantly less damage multipliers.
| Good Night and Sleep Well (The Nihility) |
|---|
 |
| For every debuff the target enemy has, the DMG dealt by the wearer increases by 12/15/18/21/24%, stacking up to 3 time(s). This effect also applies to DoT. |
Assumes debuffs at all times. Best non-five-star Light Cone, but only really a viable option if you lack any of the above, since gaining only one stack per hit is a huge loss in comparison.
| Fermata (The Nihility) |
|---|
 |
| Increases the Break Effect dealt by the wearer by 16/20/24/28/32%, and increases their DMG to enemies afflicted with Shock or Wind Shear by 16/20/24/28/32%. This also applies to DoT. |
A Free to Play option. Too restrictive and significantly behind other options.
Best teams
| Acheron fast debuff |
|---|
    |
| This team works by building speed and Energy regen on Silver Wolf and Pela to farm Acheron’s ultimate as fast as possible and debuff the enemies in the process. Fu Xuan is an excellent character. She does everything: tanks, heals, and buffs the team. If you don’t have her you can use Gepard and I believe Aventurine will work as well in the future. |
| Acheron Hanabi |
|---|
  |
| If you have Acheron at Eidolon 2, this team is the better option compared to the first. At E2 Acheron no longer needs two Nihility allies, but only 1, and that role Is fulfilled by Black Swan with her DOT, which works as a debuff for Acheron and also deals great damage. Hanabi provides buffs to the team and the Skill Point management. You can change Black Swan for Silver Wolf or Pela and Fu Xuan for Gepard or other sustain. |
| Acheron DOT |
|---|
 |
| This is the old DOT team, but instead of bringing another DOT or support you bring Acheron. She synergies greatly with the team, gaining stacks from both Black Swan and Kafka, and also has access to her double Nihility bonus. Fu Xuan can be replaced by Gepard or another sustain. |
Eidolons
Acheron’s most important Eidolons are E1 and E2. Eidolon 1 increases CRIT Rate by 18% when dealing DMG to debuffed enemies. Enemies will always be debuffed against a team that contains Acheron, and an 18% increase in Crit Rate is significant in my opinion.
Eidolon 2 is perhaps de most important one. It gives Acheron 1 stack of Slashed Dream and one enemy a stack of Crimson Knot at the start of her turn, which already is good. Furthermore, it allows Acheron to reach the full damage of her “The Abyss” trace with only one Nihility ally on the team, allowing the player to be more flexible on team building. Now if you plan on playing a team like Acheron/Kafka/Black Swan this part doesn’t matter.
Eidolon 6 is also interesting because it increases the All-Type RES PEN for the Ultimate DMG dealt by Acheron by 20%. It also turns all the damage Acheron does to Ultimate DMG, reducing the enemies’ toughness regardless of Weakness Types. While this is good, I, unfortunately, don’t have a way to test this in practice, and on paper, it seems to me a long way to get to E6 for a not-so-significant buff.
Should you summon?
Acheron is one of the most hyped characters in the game, and probably anyone who planned to pull for her already did, but if you are in doubt there are some things to consider.
If you still don’t have a DPS character Acheron is a good option, since there are plenty of F2P Nihility options for building a team with her, such as Sampo, Guinaifen, and Pela, although, besides Pela, they are not the best options.
If you have Silver Wolf, you should consider pulling for Acheron, since the two of them, together with Pela can form a great team. If you have Black Swan with Kafka, I would say that Acheron is a must-pull. The Black Swan/Kafka combo is already incredible Acheron only adds to the team. If you only have Black Swan you can still do a team with a support, especially Hanabi, or use another Nihility like Pela.
Now if you already have some DPS characters and/or desn’t have any of the 5-star Nihility characters mentioned above, you won’t benefit as much. Aventurine, which will come next banner, can be a good addition to Acheron’s team, but will not replace any of the main units. Of course, if you like the character or her design you should do what you want. No new character in this game is so bad for your account that it is unusable.
