Betrayer

"'Saving your people will not bring you peace, only makes the burden you carry worse.'- The Betrayer to the Doom Slayer."

The Betrayer, real name Valen, is the former commander of the Night Sentinels that committed treason against the realm to bring back his dead son. He is one of the supporting characters in Doom Eternal.

Background
The Betrayer used to one of the Night Sentinels commanders who led countless battles against the forces of hell. However, after his son perished in battle, he betrayed his kin to bring him back, leading to the fall of Argent D'Nur and his comrades being scattered in hell.

Doom Eternal
The Doom Slayer meets the Betrayer to retrieve the Celestial Locator to track down and kill all the Hell Priests to destabilize hell forces on Earth.