When she sensed the power of the wizard Hero, she gave him a vision of a fountain outside Erana's Garden to gain his attention. She began watching him, waiting for him to become powerful enough to be useful to her. Eventually, she appeared to him and told him of the staff that she desired. She taught him the Ritual of Release, that he might perform it when the time came.
After the Hero retrieved the artifact, Tatiana and some of her subjects appeared to him again. They demanded the Staff, but the Staff itself refused. Furious, Tatiana and her followers attacked the Hero. Using his own array of spells, he defeated each of them. He found the Heart Ritual in a glowing orb that was released upon her death -- if she did, in fact, perish.
Queen Tatiana appears in Quest for Glory IV: Shadows of Darkness, but only to the Wizard character. Her entire subplot is inaccessible to other classes.
It is not entirely confirmed, though it is assumed, that Tatiana is killed by the Wizard -- though neither she nor her subjects left corpses.