@JustinMezzell
It would be my honor! You first meet Artorias in Oolacile, where he has become consumed by the Abyss he set out to destroy. We first meet Sif guarding his grave, still his steadfast ally and protector even in death. In DS3, however, I believe you encounter Sif again.
@JustinMezzell
In the swamps at Farron, you find the body of the "old wolf of Farron", and also the Abyss Watchers Legion, a knighthood dedicated to fighting the Abyss...that were eventually consumed by it...and defeating them allows you to shape their soul into the Wolf Knight Greatsword.
@JustinMezzell
The old wolf, who gives her power to the Legion in the form of the Soul of the Blood of the Wolf, is Sif. You find her here because Farron is Oolacile, many eons later — she never left Artorias’ side, even in his death, even in hers.