Great Grey Wolf Sif

 is a boss in Dark Souls. Found in Darkroot Garden. He guards the grave of Artorias the Abysswalker, one of Gwyn's four knights.

Location
Sif can be found in Darkroot Garden behind large, glowing double doors.

Artorias of The Abyss
Sif makes an appearance in the Artorias of The Abyss DLC. He is located behind an illusionary wall after being led about by Alvina in the Chasm of The Abyss. He is found protected by a magical barrier, which was created by Artorias using his Cleansing Greatshield in order to shield Sif from the corruption of the Abyss. Killing the surrounding Humanity Phantoms will cause him to vanish and leave behind Artorias' shield. After being rescued he can be summoned during the battle against Manus.

Also, if the player saves Sif in the Chasm of the Abyss before killing Sif, a different intro will play. In it, Sif will recognize the player as they approcach and let out a whimper. The player reaches out to pet him, but he pulls away and howls mournfully, before sadly picking up Artorias' greatsword.

Strategies
The best thing the player can do is to try to get under him so he cant swing his sword at the player and then just attack him until he dies. If the player does this watch out for his slam attack. From time to time Sif will jump away from the player so the best thing to do is to wait until he attacks, and while he recovers, run under him and repeat the cycle until the player has defeated him. The fight will go easier if the player can use sorcery or pyromancy to soften him up before moving in with their melee attacks.

The player can also summon a phantom and have him or her distract Sif while the player runs under him.

Dashing Slash
Like all of Sif's attacks, this can be blocked. However, this attack hits twice; once with the sword, and if Sif's body touches the player. If the player blocks both, massive stamina damage is guaranteed.

Spining Slice
Sif switches the sword in his mouth to a straight position, and spins around twice. Does huge stamina damage if blocked, since the spin hits twice.

Sword Slam
Sif slams the sword in his mouth into the ground. Powerful, but has no tracking and poor hitbox. Attack is blockable, has no follow up attacks and has substantial recovery.

Evasive Slash
Sif will attempt to slice the Player while jumping backwards and away from the player in one motion. Has little to no starting lag. Blocking it won't give the Player an opportunity to attack, but will help the player survive.

Single Slice
Sif will do a quick chop from side to side. Good tracking and high hitbox. Possible to roll underneath it with good timing. Also does not do much damage to the stamina bar, thus it can be blocked quite easily.

Double Slice
Two slashes from side to side. Great tracking, thus very difficult to sidestep. However, the slices can be rolled under and blocked fairly comfortably without the stamina bar being fully drained.

Finishing Combo
Sif will slice twice and then finish with an overhead smash. The last attack has poor tracking and a small hitbox, so use this as an opportunity to get some hits in.