Celia is a shadow priestess who is also the founder and leader of a religious cult known as "With Light". When Dracula was destroyed in 1999, she noticed that the spiritual powers of the world had weakened, and in turn, feared that this would cause her to lose her own powers.
At one point, she learns about a young man named Soma Cruz, the main hero of the game, and that he is actually the reincarnation of Dracula. The problem is that Soma realizes what a devastating catastrophe for the world it would be if Dracula ever regained his true power again. Celia wishes to change this, however, and recruits two other men, Dario and Dmitri, telling them that they are each "potential candidates" to bring Dracula back to power. In reality, however, knowing that Soma is the only way, her true plan is to lure him to her castle in an attempt to awaken the evil lord.
Celia's fate has three different outcomes depending on the actions that the player takes in the game:
1.) After Soma defeats Dmitrii and kills Dario, Celia flees the castle and her whereabouts become unknown.
2.) After Soma defeats Dmitrii and destroys the fire demon that Celia had fused to Dario, the priestess calls him to the castle's center. Once he arrives, Celia kills a doppelganger of Mina, Soma's love, whom he believes actually to be her. Allowing his hatred to consume him, Soma becomes the Dark Lord, but immediately kills Celia for what she has done, much to her shock and dismay.
3.) After Soma defeats Dmitri and destroys the fire demon that Celia fused to Dario, the priestess calls him to the castle's center. Once he arrives, equipped with Mina's Talisman, Celia kills Mina's doppelganger. But before Soma's anger transforms him into the Dark Lord, his friend Arikado arrives and exposes her ruse. At this point, Dmitrii resurfaces and Celia realizes that there is still hope for the Dark Lord to be reborn. However, after she and Dmitrii travel to the Abyss, he betrays and sacrifices her in order to gain dominance over a powerful demon.
Despite these many opportunities, the player never engages Celia in battle at any point in the game.