Petrus of Thorolund

"Fool...What were you thinking? Too bad for you, I'm a wolf in sheep's clothing. Best of luck as a Hollow! Gah hah hah hah hah!"

- Petrus should he kill the player.

Petrus of Thorolund is a supporting antagonist in Dark Souls.

He was voiced by Sean Barrett.

Biography
Petrus is from the Way of White covenant, a group based on following Lord Gwyn in kindling bonfires to sustain power of the gods. He can be found at Firelink Shrine, near the lift to the Undead Parish. Initially he demands that he wants to keep a distance from the player, but gives them a Copper Coin to show that it isn't personal. Talking to him a third time, he will ask if the player wants to join the Way of Light covenant. Should they accept he will sell them Miracles. When prompted enough times, Petrus reveals he is on a classified undead mission with a maiden named Reah and her bodyguards Vince and Nico.

After the Capra Demon in Undead Burg is defeated, Petrus is joined by Reah and her companions, saying only farewells to the player. They are gone the next time the player returns to Firelink Shrine, but the next, Petrus is all alone. He explains that he got lost from Reah, regretting having lost her despite his sworn oath to protect her.

Talking to Lautrec about the mission, he reveals that Petrus didn't get lost, instead he abandoned his comrades to the monsters in the Tomb of the Giants. If the player talks to Petrus about this, he tries to persuade them that it was a coincidence that Reah fell down a pit and that Vince and Nico have went hollow, taunting the player that they have no chance to save Reah.

This is subverted if the player actually finds Reah in the Tomb of the Giants and defeats the hollow Vince and Nico, she will move to a shrine in the church of the Undead Parish. If the player has not bought all of Reah's Miracles (resulting in her being taking by Channelers to the Duke's Archives), killing two major bosses makes Petrus realize that she is still alive, resulting in him killing her. Only by killing him first will he not be able to kill Reah. Should Reah have died from Petrus, he drops her Ivory Talisman upon death.

Trivia

 * Petrus was originally going to have to be rescued from a necromancer in the Catacombs before he showed up at Firelink Shrine.
 * Killing Petrus before Reah and her bodyguards arrival to Firelink Shrine turns them all hostile immediately. Paying Oswald for absolving a sin will not turn them back friendly.