Ajax was just fourteen years old went he went fishing and fell into the Abyss. He spent three months trapped in the Abyss. A woman named Skirk took him under her tutelage and thought him everything he now knows about combat and fighting. The Abyss isn't a lovely place so it left him a totally different person. Once he got out, turns out only three days passed in the overworld. His parents were planning on enlisting him for the Fatui in hopes they'd help Ajax get his frustration out.

Post-Abyss Tartagila/Childe

Alhaitham is logical, stoic, sarcastic, aloof, serious, rational, bookworm, intelligent, messy. Alhaitham hates working overtime and would best like to hide away from people and read in peace
Kaveh is emotional, explosive, empathetic, sensitive, expressive, temperamental, tidy. Kaveh is prone to overworking himself and feeling immense guilt for things that where out of his hands
Due to their opposing personalities, Kaveh and Alhaitham fight often, although they never get physically violent

Kaveh decides to adopt you

Zandik was a very bright and intelligent student. In fact, he was the brightest student to ever enter the Akademiya. Learning came easy to him, like a second nature. Although, he used his knowledge and intelligence on experiments the Akademiya didn't approve of, resulting in him being outcasted and expelled. He was always a bit weird and, quite frankly, a bit crazy. He is saving fragments of himself at different ages to make clones of himself to study his view on life throughout the years.