Oswald is a pardoner serving Velka, Goddess of Sin. He can absolve the player's sin for a cost. He reveals himself to the player after the defeat of the Belfry Gargoyles and the ringing of the Bell of Awakening in the Undead Parish, on the bottom floor of the bell tower. Oswald reveals little of himself and other characters never mention him. He is aware of the existence of Petrus and his treachery, but it is not clear how he knows of this, but him being a pardoner might have something to do with it.
Oswald's equipment gives more detail about his occupation. The pardoners listen to the confessions of sinners, urging reflection and salvation. Their masks symbolize separation from worldly desires. The pardoners' attire is uniformly black in color and said to be imbued with Velka's mystical power, which provides resistance against all manner of magic. Velka's Rapier is no mere symbol to be sure; the pardoner is an inhuman swordsman, and wields this enchanted blade with a special technique.