Guide
How the kit works
Before a fight, Mold of Idolatry creates a dimension for 10 seconds and Taunts nearby enemies. Entering battle with enemies inside it gives a 100% base chance to reduce each enemy's SPD by 15% for two turns. Only one allied Dimension Effect can exist at a time.
Put debuffs on your target, then use Intellectual Midwifery. It deals Imaginary DMG equal to 150% of Dr. Ratio's ATK. Cogito, Ergo Sum gives that Skill a 40% fixed chance to launch a Follow-Up ATK for 270% of his ATK, plus 20 percentage points per debuff. If the target is defeated before this follow-up triggers, it goes to a random enemy instead.
Inference gives the Skill a 100% base chance to reduce the target's Effect RES by 10% for two turns. Summation grants 2.5% CRIT Rate and 5% CRIT DMG per debuff when the Skill is used, up to six stacks. With at least three debuffs on a target, Deduction raises Dr. Ratio's damage to it by 10% per debuff, up to 50%.
Use Syllogistic Paradox on the enemy you want the team to attack. It deals 240% of his ATK as Imaginary DMG and applies Wiseman's Folly. Teammate attacks on that target trigger his Talent's Follow-Up ATK up to twice. A new Ultimate changes the marked target and resets the trigger count. Mind is Might deals 100% of his ATK to one enemy.
Build and why
The leading relic choice is four-piece Pioneer Diver of Dead Waters. Its two-piece effect raises damage against debuffed enemies by 12%, and the four-piece adds CRIT Rate and CRIT DMG against enemies with enough debuffs. After Dr. Ratio inflicts a debuff, those four-piece effects double for one turn. Four-piece Wastelander of Banditry Desert is an alternative, though its CRIT DMG bonus requires an Imprisoned target.
For planar ornaments, use Duran, Dynasty of Running Wolves. Ally Follow-Up ATKs build Merit stacks that increase the wearer's Follow-Up ATK damage, with 25% CRIT DMG at five stacks. Inert Salsotto is another option: it gives CRIT Rate and, at 50% CRIT Rate, increases Ultimate and Follow-Up ATK damage.
Use CRIT Rate or CRIT DMG on the body, SPD on the feet, Imaginary DMG Boost on the sphere and ATK Percentage on the rope. For substats, look for CRIT Rate first, then CRIT DMG, ATK Percentage and SPD. Account for the CRIT Rate Dr. Ratio gains from his Traces and equipment when choosing the body piece.
Baptism of Pure Thought is the first Light Cone choice. Debuffs increase its CRIT DMG bonus, and using Ultimate grants a damage increase and lets Follow-Up ATKs ignore some DEF. Worrisome, Blissful follows it, with CRIT Rate, Follow-Up ATK damage and Tame stacks that increase allies' CRIT DMG against the target. The Finale of a Lie is another option; Cruising in the Stellar Sea gives CRIT Rate if you use the game's listed alternative.
Leveling priority
Follow the game's order: level Cogito, Ergo Sum first, then Intellectual Midwifery, Syllogistic Paradox and Mind is Might. The Talent comes first because its Follow-Up ATK is triggered through both the Skill and the Ultimate's mark. The Basic is last because the rest of the kit centers on Skill and follow-ups.
For full ascension, you need 308,000 Credit, 65 Suppressing Edict, and 15 each of Thief's Instinct, Usurper's Scheme and Conqueror's Will.
For all skills, prepare 3,000,000 Credit, 8 Tracks of Destiny, 18 Arrow of the Beast Hunter, 69 Arrow of the Demon Slayer, 139 Arrow of the Starchaser and 12 Past Evils of the Borehole Planet Disaster. You also need 41 Thief's Instinct, 56 Usurper's Scheme and 58 Conqueror's Will.
Eidolons worth it
For the largest upgrades to consider, Vincit Omnia Veritas raises the Talent's Follow-Up ATK damage by 50% and adds one Wiseman's Folly trigger. It is the final Eidolon, so reaching it requires all the earlier ones.
The Divine Is in the Details is an earlier damage option: each debuff adds Imaginary Additional DMG equal to 20% of ATK when the Talent's Follow-Up ATK hits, up to four times per follow-up. Pride Comes Before a Fall raises Summation's stack limit by four and starts battle with four stacks, provided the Trace is unlocked.
If you do not plan to go beyond E2, stopping there lets you skip the later upgrades. Know Thyself and Sic Itur Ad Astra raise skill levels, while Ignorance Is Blight restores 15 Energy when the Talent triggers. They remain necessary steps if you want E6.
Common mistakes
Do not assume every Skill will trigger a follow-up. Without debuffs, the Talent's fixed chance is 40%; three debuffs bring it to 100%. Inference has a base chance to apply its Effect RES reduction, so do not treat that debuff as guaranteed.
Do not spend teammate attacks on other enemies while expecting them to trigger Wiseman's Folly. Attack the marked target, and be careful about using another Ultimate before its two triggers are spent: the new mark resets the count and affects only the latest target.
Do not build only for ATK. Dr. Ratio benefits from CRIT stats, and his listed build also uses SPD and Imaginary DMG Boost. Likewise, check the conditions on your sets: Inert Salsotto needs 50% CRIT Rate for its damage bonus, while Wastelander of Banditry Desert needs Imprisonment for its CRIT DMG bonus.
