When you reach the wyrmway area and interact with ansur's corpse, you'll trigger the big identity reveal about the emperor being balduran. The timing of this discovery is pretty flexible since you can technically push through most of the main story without ever learning this detail. Most players find it during their exploration phase after reaching act 3, but interestingly the game doesn't force you into this revelation.

What's really crucial to understand is how the actual gameplay mechanics work around this - your major decision points with the emperor aren't actually tied to knowing his true identity. The key moments where you'll need to make choices about trusting him or siding with orpheus depend more on your immediate interactions and how you feel about his current actions. Maybe interesting to note that during confrontations, his dialogue options and behavior patterns stay consistent whether you've discovered his identity or not

The real tactical consideration here is that this knowledge gives you extra context for understanding his motivations, especially regarding the city and the astral-touched tadpole situation, but it won't lock you out of any particular ending paths or significantly alter your available choices. Just keep in mind that your relationship status with him updates based on your current actions rather than your knowledge of his past