The Facts:

The MC doesn't know how young they were when they were kidnapped and trained up to be an assassin, but it was very young.

The MC has no memory of who they were before the Tubal Compound, a place specifically designed to create killers.

They grew up with about two dozen other children in their "class", each of them numbered; MC was once called "29".

The MC killed their first person around twelve to thirteen. It was another child, during a culling.

After this trial, they began to train with the older children from their part of the compound and begin to specialise.

The MC knows multiple languages, with varying degrees of literacy, including ASL.

The MC, due to their talents, was hired out at a mere fifteen for their first job.

For reasons unknown to them, at eighteen the Tubal Compound went up in flames and the organisation who ran it fell apart. The MC and many others took the chance to escape.

For ten years the MC was an independent contractor, building up their name and reputation throughout the criminal world as an assassin without equal.

This roughly puts the MC in their mid-thirties.

The MC had never considered another life for themself- until they met the child that changed their life forever.

They learnt what love was through their child.

The MC has never experienced romantic love in their lives.

Customisation:

Whilst I will try and include as many of these as possible, I am a baby coder right now, so some options may not be available at the start, and as a WIP these could even change along the way;

Appearance! Skin colour, hair, eyes, height, weight, skin features like moles, scars, tattoos, genitals etc.

Ethnicity and nationality! It will be planned that your ethnicity is going to be tied to your skin colour (if that wasn't obvious), but you will know which country you were taken from.

Full name! When you left the compound, you chose a completely new identity for yourself.

Sex and gender! Whether you continued to identify with the gender you were raised under or took the chance to transition once you were free, that is entirely up to you.

Sexuality! So, this is customisable, however not in a simple choice way. Because of the life the MC has lived, I am exploring the way I can have them consider their sexuality through this story. For example, if you decide to make all the main cast male, I want that to register and for the MC to realise "Oh, I must like men!".

A permanent old injury! You've had a long, intense career as a killer, even someone like you has not been able to get away completely unscathed. Do you have only partial hearing in one ear? Are some of your fingers numb from nerve damage? Is one of your eyes wonky?

A hobby! You have a lot of time on your hands now, try and find something to do to make the days go faster.

Your specialisation! Decide how you used to usually kill your targets. Poison? Explosives? Were you a Black Widow and seduced your targets into complacency, or did you prefer an upfront assault?

Your moniker! Either pick from some options or make up your own moniker that was given you during your career.