Dr. Ratio — Honkai Star Rail Character Guide

Imaginary Hunt DPS · MoC T5 · PF T5 · AS T5

Overview

Follow-up DPS who requires 3+ debuffs on enemies to guarantee Talent triggers and activate his A6 damage bonus. Accumulates permanent CRIT buffs via Summation and deals heavy single-target damage, but falls behind newer FUA carries.

Follow-up Attack Hunt DPS who builds permanent CRIT stacks via Summation and relies on enemies having 3+ debuffs to guarantee Talent follow-up triggers. Skill is the primary action each turn, triggering a 270% ATK follow-up when the target has enough debuffs. Ultimate marks a target with Wiseman's Folly, causing ally attacks to trigger additional follow-ups. Damage output scales heavily with debuff count on enemies — both follow-up rate and A6 DMG bonus depend on it.

Key Mechanics

Debuff threshold of 3 is the critical breakpoint — it guarantees 100% follow-up rate from Talent and activates A6 DMG bonus (30% at 3 debuffs, 50% at 5). Below 3 debuffs, follow-up rate drops to 80%/60%/40% and A6 is inactive.
Summation stacks are permanent and accumulate across different targets. After 2 Skill uses against 3-debuff enemies, full 6 stacks provide 15% CRIT Rate and 30% CRIT DMG for the rest of battle. This significantly relaxes endgame CRIT stat requirements.
Highest base ATK in the game (776) makes ATK% buffs and bonuses scale exceptionally well on Dr. Ratio compared to other characters.
Energy economy is surprisingly strong for a 140-cost Ultimate — each Skill with follow-up generates 35 Energy, and Wiseman's Folly follow-ups add 5 Energy each (10 total from 2 procs). Typical 3-turn Ultimate cycle with consistent follow-ups.
Toughness damage is exceptional for a Hunt character — each Skill + follow-up deals 30 Toughness (equivalent to most Ultimates), enabling faster Weakness Breaks on single targets.

Best Teams for Dr. Ratio

Debuff Hypercarry

Ratio as sole DPS with a dedicated debuffer and a hypercarry buffer. The debuffer handles 2-3 of the required debuffs (Silver Wolf, Jiaoqiu, or Pela), freeing the sustain and amplifier slots for pure damage buffs. Structure enables 100% follow-up rate and the full A6 DMG bonus at 3-5 debuffs. Most accessible composition with widest sustain options.

S-tier: Dr. Ratio, Silver Wolf, Sunday, Dan Heng • Permansor Terrae
S-tier: Dr. Ratio, Jiaoqiu, Sunday, Dan Heng • Permansor Terrae
A-tier: Dr. Ratio, Pela, Sunday, Aventurine

FUA Dual-Carry

Ratio paired with a second FUA damage dealer (Topaz or Moze) under Robin's Concerto buffs. The FUA partner provides debuffs for Ratio while also dealing substantial personal damage. Robin's Ultimate advances all allies and grants 72% FUA DMG bonus across the board. A sustain with debuffs (Aventurine) covers the remaining debuff gap.

S-tier: Dr. Ratio, Topaz & Numby, Robin, Aventurine
A-tier: Dr. Ratio, Topaz & Numby, Robin, Dan Heng • Permansor Terrae
A-tier: Dr. Ratio, Moze, Robin, Aventurine

Cipher Hypercarry

Ratio paired with Cipher as both debuffer and additional damage dealer. Cipher's Vulnerability debuff counts toward Ratio's threshold while contributing True DMG output. Enables strong single-target focused teams where Cipher handles the debuff requirement, leaving the third slot open for a pure buffer like Sunday or Robin.

S-tier: Dr. Ratio, Cipher, Sunday, Dan Heng • Permansor Terrae
A-tier: Dr. Ratio, Cipher, Robin, Aventurine

Best Teammates

DPS Partners: Topaz & Numby (S), Moze (A)

Amplifiers: Robin (S), Silver Wolf (S+), Jiaoqiu (S), Sunday (S+), Cipher (A), Tribbie (A), Pela (A), Ruan Mei (B), Bronya (C), Tingyun (C)

Sustains: Dan Heng • Permansor Terrae (S+), Aventurine (S), Huohuo (A), Gallagher (B), Luocha (B)

Investment Priority

LC S1 — Signature provides CRIT DMG, Disputation DMG buff, and DEF ignore on follow-ups after Ultimate — the largest single performance jump for Ratio and the recommended first target.
E2 — Adds up to 80% ATK as additional DMG per follow-up at 4 debuffs — a massive multiplier increase. Best eidolon stopping point; E1 is on the way but not a recommended standalone stop.
E1 — Raises Summation cap to 10 stacks and grants 4 starting stacks, providing 10% CRIT Rate and 20% CRIT DMG from turn one. Primarily valuable on the way to E2.

Best Relics

Recommended: pioneer-diver-of-dead-waters with duran-dynasty-of-running-wolves

Stat targets: SPD 134 / 143 / 161, CRIT Rate 90-100% in-combat, CRIT DMG 180-200%+, ATK 2700+

Main stats: Body: CRIT Rate / CRIT DMG · Feet: SPD / ATK% · Sphere: Imaginary DMG / ATK% · Rope: ATK%

Important Notes

Signature LC provides 16%+ performance gap over Cruising at S5 — largest single investment gain available.
Requires 3+ debuffs on target for 100% follow-up trigger rate — team building is constrained by this threshold.
A4 Effect RES debuff applies after the follow-up check — first Skill on a fresh enemy has lower follow-up probability.
Wiseman's Folly is lost if the target dies before triggers are expended — can waste Ultimate value in fast clears.
Overtaken by Feixiao as the premier FUA DPS — Ratio remains competitive but is no longer the top-tier option.
Needs 6 Summation stacks for full CRIT buffs (15% CRIT Rate, 30% CRIT DMG) — minor ramp time at start of battle (resolved by E1).