Prior to the Jihad Reginald VanJaster was a mediocre MechWarrior in Solaris VII. When the Word of Blake invaded Solaris, he joined the resistance (not confirmed if the SHDL or any other group) and gained so much combat experience that it made him one of the most skilled MechWarriors the resistance had. Four days before the Word's withdrawal from Solaris, he learned of the murder of his wife, Melissa, at their hands. After this, the official theory says that he suffered some sort of mental breakdown. After that success, he started killing any Word of Blake he found, and indeed anyone who tried to stop him (for example some of his resistance comrades).
The end of the occupation didn't stop his rampage. His next target was the newly established government that he accused of being Blakist patsies. He was able to leave Solaris soon afterwards and let his crusade deeper into the crumbling Blake Protectorate.
The end of the Jihad did not stop him. After the formation of the Republic of the Sphere he started attacking planets on Prefectures VIII and IX, claiming the Republic to be a fake government and Devlin Stone a Word of Blake plant. He has shown no problem attacking unarmed civilians.
The Republic of the Sphere has been trying to catch him, but his pattern is very erratic, most probably because he can only catch those transports that ask no questions.
He prefers close combat because of his 'Mech configuration.
- Experimental Technical Readout: Most Wanted, p. 5 "BL-X-KNT Black Knight “Red Reaper”"