Hennig joined Crystal Dynamics, marking a significant turning point in her career. This is where she began to significantly influence narrative design.

She served as a designer and writer on the original Legacy of Kain, beginning the popular franchise. She established many of the series' major themes and lore.

Hennig directed and wrote Legacy of Kain: Soul Reaver, a critically acclaimed action-adventure game that is considered one of the most important games in the series. Its storytelling, world-building, and voice acting were highly praised.

Hennig continued her work on the series as director and writer for Legacy of Kain: Soul Reaver 2, building on the narrative and expanding the world of Nosgoth.

Hennig was involved in the early stages of Legacy of Kain: Defiance before moving to Naughty Dog. While her direct influence is less prominent than in previous entries, the groundwork she laid was vital to the game's completion.