You may not think it to look at him how, but this man was once the Mentor of a powerful branch of the Assassins - the Colonial Brotherhood.
Achilles' life before he was an Assassin isn't well documented - it seems that most of the records were destroyed when the Templars nearly wiped out the order in 1763.
From what I do have, Achilles was recruited in the mid-1730s and became a Mentor in 1746. He had a gift for both recruitment and organization, so before long was head of a crew of Assassins that spanned the colonies and much of the frontier. Achilles strengthened the ties between the order and the nations of the Iroquois confederacy, particularly the Kanien'kehá:ka, though as far as our records show, Connor is the first Native American to actually become an Assassin.