Tylos Rubio

Tylos Rubio was an Ultramarines Librarian of the 21st whom Guilliman had already chained under Nikaea. Garro unchained him on Calth to save a city, then recruited him as the first Knight-Errant. Rubio had refused to leave his brothers until the Word Bearers made staying a different kind of suicide, and even then he wanted an order from the Emperor. Garro stood the line with him until the order became obvious.

Malcador took the Codicier into grey and used that unchained gift as a template. Rubio was one of the eight who later formed the core of the Grey Knights, a XIII Legion scholar rewritten into a weapon against the thing Calth had shoved through the sky.

He began as a man who had put his hood away because Terra said so. He ended as proof that Terra would take the hood back the moment the theoretical failed. The 21st Company lost a librarian. The Imperium gained a prototype.