I'll make it short and simple.

The Wayback Machine is a website that contains the archive history of other websites themselves, later archived again per time period or request.
Oldest websites were archived here in 1996 and what remains of them as archives can still be navigated to this day.

The most recent archive of Spiral Knight's Wiki was saved around June 8th. It appears to be fully functional.
https://web.archive.org/web/20170608021436/http://wiki.spiralknights.com...

As far as I can see, only some of the embedded images are missing. But it sure is better than nothing.