Artirus was a Gladiator during Roman Empire (judging by his helmet), and one of Edmond Vade's students after his death. He appeared in the arc "Those that run"
As a Gladiator in the Roman Empire he fought againts other ones in the Colosseum, probably died during a fight he managed to escape Jack for a long time before joining Edmond Vade's army as student.
ps= let's not forget that "Those that run" is set into modern time, while Artirus is clearly shown as an ancient Gladiator, that's why it seems that he escaped Jack for a long time.
After being sent to Hell and Judgement, as he made the pact to join Rework's army, he became himself a Rework, this is seen in one of the last scenes of the story.