User blog comment:Ornsteinthedarkhorse/Four Knights of Gwyn/@comment-4511886-20141226175827

I don't think they actually directly worked together that much. Ornstein, Gough and Ciaran are commanders of the Four Knights, Dragon Slayers (archers) and "Lord's Blades" (assassins) of Gwyn's army. Artorias is seemingly, and fittingly, a lone wolf swordsman, little more than an adventurer tied to an army.

While all of them may have fought them, only Gough and Ornstein are actually proven to have fought the dragons. The other two have no descriptions or dialogue that makes mention of them even being part of the army during the war against the dragons.

Ciaran was most likely recruited after the war, to assassinate Gwyn's more peaceful opponents. People like politicians, rebellion leaders and the like.

Artorias doesn't appear to be anything more than an adventurer in terms of his deeds. Perhaps he was employed by Gwyn as a way to keep the soldiers' morale up, knowing they had such a warrior on their side. His abilities seem to do little good within a unit of soldiers, especially if they were truly unmatched. Come to think of it, none of his deeds even makes mention of any warriors present except for him and Sif.