Maybe just put a warning on top.
We do not need to delete the archives. Much of EToD and several not-EToD conception are based off of archived "Tale of Diep" content. (For example, Triskaidekaphobia is a Polygon Disciple, and at least half of all of EToD's content would have copious amounts of unfixable red links if we delete the archives, including Triska.) I propose that only a special tophat is necessary. The text goes as follows:
"This project is no longer associated with Diep.io. This is an old version of a game idea, and will probably not return to this wiki anytime soon. Here is the link to the discord for ATWNM, the new name for this project. These are being kept for the sole purpose of allowing Fanon built upon old concepts in ToD that were removed during the name change to continue to stay and form, such as this project by diepmon. Thank you for your cooperation."
EDIT: the bold is not permanent, and will be replaced by an external link to the ATWNM discord with the text "Here."