You did many things in Oolacile, after realizing Dusk's disappearance, you searched for her by the lake where you first found her, soon being pulled back in time to the events of the Abyss. During your journey in Oolacile, you defeated the knight Artorias who was already corrupted by the Abyss, and... you were the one who killed Manus the Father of the Abyss and saved Princess Dusk.

But even so, the one who got all the credit was Artorias and you, it was never even mentioned or said. At least Dusk was safe and when you returned to the lake where you summoned her to talk, she appeared with great happiness to tell you her new news.

"...This may strike thine ear as somewhat peculiar, but...Long ago, in my homeland of Oolacile, I was beset by a creature from the Abyss. I would have perished then, were it not for the great knight Artorias. In truth, I saw little of what transpired, for mine senses were already fled! But even still, there was something about Artorias... A certain balance of the humours...That quite perfectly fits your semblance. Heavens, could it be that... ...Oh, dear me. That was Oolacile, many centuries ago. Please excuse my fanciful musings."