Imagine a sick Isolde Reverse: 1999 layout here
You'll get this instead, till I get inspired to deco this URL..
UPD.. I lied. This wont be about Isolde anymore. I have Dottore brainrot and I find a way to make everything about him.

Overall description
Isolde is a Sub-DPS that is primarily designed for Reality Damage dmg dealers who do Crit-Focused Damage. Isolde has a variety of buffs and debuffs and I love her a lot. I would be nothing without her buffs.
She's F2P friendly too, you don't really need her portraits, but her P1 & P3 are good.
I use her signature psycube but Blasphemer of the Night & Yearning Desire are good alternatives.
Ultimate : "Choking on Blood"
( Shamelessly took this info from her Wiki)
Mass Debuff. Inflicts 5 stacks of [Burn] on all enemies, and additional 5 stacks of [Burn] on the main target, at the same time, grants 1 stack of [Rousing Morale] to all allies, and then casts [Intermezzo] as a follow-up attack on the targets. For every excess stack of [Burn] on the main target, this [Intermezzo] gains Incantation Might +15%.
Buffs / Debuffs :
3 stacks of preignition to all allies at the beginning of each round
1 stack of Power Burst to all allies at the beginning of each round (Finale)
1 stack of Rousing Morale to all allies after using her Ultimate
25/35/50% CRIT DEF Shred
20%(25% with burn) Reality DEF Shred
++ Big amount of personal damage bcz of Penetration boost and a high % on Debuff skill.
Teams or whatever :
In my OLD team, I used her with A Knight, Tooth Fairy & Bkornblume. Mainly for her buffs / debuffs and not so much for DMG, since A Knight is the main DPS in this team.
NEW team is A Knight, Melania, Isolde & any healer (I use Tooth Fairy as always). A Knight mains plsss this team is so good. A Knight does an insta ultimate dealt at the start of every round, Melania acts as a subdps & Isolde deals buffs for both of then + debuffs enemies... If ur A Knight build is good u can deal 500k or more of dmg trustttt.
A more Isolde-centric team is Isolde, Beryl, Fatutu & Flutterpage. Isolde is really good as a buffer and debuffer for Beryl in this team and also increases overall dmg with her ultimate.
Ironically, the current best Kakania teams don't include Isolde...
Bkornblume is kinda like the 5* version of Isolde, you could use her instead of Isolde incase you don't have her. (Though, why would you be reading this is you don't?)
Shamane is also a similar character to Isolde, but he deals less DMG than her. I'm pretty sure there's newer characters u could use to replace Isolde in teams.
++ Characters that pair well with Isolde :
DPS : Spathodea, Jiu Niangzhi, Jessica & Any Reality-DMG dealer DPS tbh.
Sub-DPS / Supports : 37, Getian, and some I'm forgetting..
Healers : Honestly, apart from Tooth Fairy I don't know which healers work well with Isolde.

Ough...... Lesbians make me sick.
This took me way more than 30 secs Okay, I wrote this all by memory and transcribing text from the wiki. Owned by @ anatomy NS.