Just watched a video of a full playthrough of map 20, because I haven't been able to beat it yet, and this feels like a look back on everything that came before. The aesthetics for the most part are very new Sunder, with a stronger sense of "this is a specific place", but it's also the map with the most obvious Ribbiks influences, with the dark metal contrasted with colored lights, and the final arena could have come straight out of Sunlust. The gameplay of the main "city" portion reminds me a lot of old Sunder however, with the central building feeling like a redo of Hive Mother's central arena, now including the actual Hive Mother, and other parts being reminiscent of fights in The Cage, Precarious and the big open arenas filled to the brim with hordes of monsters, with the switches needed to open progression tucked away at the backs of monster closets in maps like Hollow Icon, The Furnace or the final room of Metal Descendants. All in all, very atmospheric and I can't wait to actually finish it, however long it will take.