Overview

With the introduction of C-93, Girls' Frontline skill descriptions have reached lengths never before thought possible and are now giving even the most verbose MTG cards a run for their money. Fortunately, it's not nearly as complicated as it may appear at first glance.

• In practice, you can treat C-93 as a hybrid Damage/RoF buffer HG who's a little worse than Grizzly normally but around or above the level of SAA Mod if properly supported. (We don't talk about her stealth bomber-shaped tile buff.)

So what does "properly supported" mean? C-93's passive will proc whenever your units are debuffed. There are some fairly reliable ways to debuff yourself (excluding debuffs that are very debilitating or those that on dolls who don't benefit from C-93's RoF buffs like AUG):

• Anna Graem's Active Skill
• Px4 Storm's Active Skill
• Preiya and Camilla's Active Skill
• Dorothy's same-column skill effects
• M4A1Mod, K31, and IWS 2000's Active Skills

C-93's full potential is easy to bring out with either Anna Graem or Px4 Storm - both affect the entire team and the debuffs largely don't matter or are easy to counteract. While you can theoretically use her with M4A1Mod or IWS2000, this isn't necessarily the best idea since there are other dolls that provide better support than C-93 in that type of "double jupiter" team. 

Sure, you can use C-93 to offset the Parachute Fairy penalty slightly since they do count as debuffs. You're still going to feel the debuffs though. 

How does it actually work?

You don't really need to know this to teambuild her, but since you asked:

1. C-93's passive constantly checks T-Dolls on the field and grants any debuffed T-Dolls an 8% RoF buff for 4 seconds. 
2. This can't apply to the same T-Doll more than once every 3 seconds and doesn't stack (but instead refreshes duration to 4s). 
   • A very long debuff can proc this passive multiple times. 
3. The active portion is a "channeled skill".
   • C-93 immediately buffs every T-Doll with 18% Damage. 
   • C-93 then distributes RoF stacks in descending order of % damage dealt (MVP gets one first, then 2nd place DPS, etc.).
   • This is not instant and takes at least 15 frames (0.5s) per cast, is interrupted if C-93 moves (since she has to stand still to distribute the stacks), and C-93 cannot gain any passive stacks during this channeling animation. Think El Clear's skill - this is pretty much like that. 
   • If every doll has been buffed already and C-93 has stacks left, repeat again from the top of the list. 
4. When C-93 finishes distributing her stacks into RoF buffs, she gains 3 butterflies immediately ("once skill ends" refers to her casting animation, not the buff duration) and can start stacking it from debuff effects again.