Argall was the ruler of the Viltrumite Empire before Grand Regent Thragg and it was later determined his bloodline connected directly to that of Nolan & Mark Grayson. According to Thragg, Thaedus who was the former leader of the Coalition of Planets was the one who killed Lord Argall.
Powers & Abilities
Lord Argall is a Viltrumite so he would have all the same powers as them; Super Strength, Super Speed, Flight, Healing, Invulnerability as well as being a well trained combatant.
Lord Argall and his bloodline are also supposed to be highly resistant to the deadly Scourge Virus which killed nearly all of the Viltrumite people.