Ornstein is believed to be the captain of the Four Knights of Gwyn.
He stands guard in the Anor Londo cathedral, alongside Executioner Smough, protecting the princess Gwynevere.
Lord Gwyn split some of his Lord Soul and gave it to his four most trusted knights, including Ornstein's Soul:
Soul of Ornstein, Dragonslayer Knight who guards the cathedral in the forsaken city of Anor Londo.
Special beings have special souls. Lord Gwyn granted this soul to his four most trusted knights.
Gwyn also gave them special rings; Ornstein receiving the Leo Ring:
One of the special rings granted to the four knights of Gwyn.
The Leo Ring belonged to Ornstein the Dragonslayer.
This ring strengthens counters with pierce weapons.
His lugged spear is said to have sliced a boulder in two.