Top of the Food Chain - Kingdom Death Phoenix and Watcher

The Phoenix and Watcher encompass a lot of what Kingdom Death is, in my opinion--

The Phoenix is just a huge monster, who's something terrible to fight and look epic on the table, plus, y'know, covered in extra body parts.

And then there's the Watcher, made of the iconic lanterns in the setting, with all of the sense of inevitable doom that a boss should have.