What word describes something that just takes over all things—like if you have a religion that usurps all aspects of life?

The word "all-encompassing" captures the idea of something that takes over all aspects of life. However, if you’re looking for something stronger, "totalizing" or "pervasive" could work. If it’s something that dominates aggressively, "consuming" or "imperialistic" might fit.

For a religious or ideological system that absorbs everything, "omnipresent," "monolithic," or "hegemonic" might also be good choices.