This is a recap of the second half of the first season. It cuts out about an hour of content and adds some minor scenes, most notably in the final fight which clarify parts of the plot. I would still recommend watching the first season in its entirety if you're planning to watch the rest of Overlord, but if you're tight on time, or just looking for a rewatch, this is a pretty decent recap. It mostly cuts out narrative worldbuilding and some character interactions, resulting in 90 minutes of back to back action. You won't be missing that much by substituting The Undead King andThe Dark Hero for season one. The most discarded elements are those involving the adventurer's guild and some Nazarick politics.