Uni-the-Unicorn!
Hero
You missed where it got help from two other party members: pass without a trace and hasteRanger/barbarian/fighter/warlock. A very MAD oriented character. I am very very curious about your character development and how it worked out. We did some of these 4 classes characters in our white room analysis and they always were suboptimal. If such a character can take on a CR23 alone, I am very intrigued.