There is indeed some content between the first and second seasons of Overlord because in the first episode of the second season, Shatia and White Dragon are still living in the past and the memories of White Dragon contain some content about Shatia and White Dragon. This information may have an impact on the following plot. In addition, there are some different plots and characters in the second season compared to the first season. This information may also appear in White Dragon's memories.
It ends at a specific chapter, but I can't recall exactly. You might want to check some manga forums or dedicated Overlord fan sites for the precise details.
The light novel that serves as the basis for Overlord Season 4 is the ongoing series by Kugane Maruyama. It has a rich and complex storyline that the anime adaptation tries to capture faithfully.
The ending of season 3 of Overlord corresponds to a specific point in the light novel series. But exactly which one might vary depending on the adaptation and how closely it follows the original source.
Season 3 of Overlord ended at a specific point in the novel that was crucial for the development of the story. But I can't recall the exact chapter or volume right now.
Overlord Season 4's placement in the manga isn't straightforward. It depends on how the production team chose to adapt and sequence the storylines. Sometimes they might compress or expand certain parts for the anime.
One great 'Dragon Age Overlord' fanfiction is 'The Dark Lord's Ascent'. It has a really interesting take on the world of Dragon Age combined with the concept of an overlord. The character development is well - done and the plot keeps you hooked from start to finish.