His weapon of choice for contracts is magic, stating that "there is a spell for every circumstance." He is the self-described "cranky old uncle" of the Dark Brotherhood family at the Sanctuary.
When asked about himself, he says he was a child prodigy. Casting simple spells by one, completing complex incantations by three, resurrecting corpses by seven, and accidentally burning down his family home due to some lightning that got "out of control," but he says nobody should worry, because he mastered all magic just after that happened.
He then went on to teach at the College of Winterhold for two years, but left due to none of the mages there "truly appreciating the Destruction school." This led him to join the Dark Brotherhood. When asked for help about a contract from Nazir, he says that methods used today are overrated and follows up with, "Just do what I do. Walk up to them, introduce yourself, melt all their skin off, and run like the wind. Works every time." He is also the first member to welcome Cicero into the sanctuary.
If asked for advice during Bound Until Death, he will reveal that he was married at one point but murdered his wife during their honeymoon over the temperature of his bath water.
At first Festus is rude and arrogant towards the Dragonborn, but upon following his instructions in the Recipe for Disaster quest, he says, "I believe I was wrong about you."
When the Dragonborn returns to the Sanctuary during the Penitus Oculatus attack, Krex is the first of the Dark Brotherhood that is found, outside the sanctuary, his body riddled with 18 arrows that are pinning him to a tree; although, his face cannot be seen.
- Festus may be a reference to two characters who share his name from the Fallout series (which is also made by Bethesda).
- Festus is Latin for joyous, which may be a joke upon his curmudgeonly nature.
- After being found dead at the Sanctuary, his Shrouded Robes cannot be taken from his body.
- The Elder Scrolls V: Skyrim (First appearance)