Certain quests, that are marked out, may be locked or unlocked by saving /sacrificing Archfiends indicated by the arrows in the menu. To unlock this pact, you need to fight Magusar, and win the fight.
Saving the Illecebra
|I. Innocence· II. Desire · III. Reparation · IV. Atonement · V. Envy · VI. Pride · VII. Judgment · VIII. Remorse ·|