How to ‘select all’ tags?

I am sorting out an archive for a web comic style site and want to re-post every things one by one from the beginning. However, none of the comic have a category (they are published as comics), and there isn’t a single tag that they all use. There is a ‘chapter’ they are all in as part of the webcomic plugin I’m using, but that obviously isn’t an option in the plug-in.

Thanks!