Does this mean that I can't have a wiki at malleus-commons.sturmkrieg.com?
If you mean you wish to redirect your own subdomain to a Wikkii subdomain and mask the URL of the Wikkii subdomain, technically, should be able to do this if you have access to the DNS settings on your current host.
Your domain registrar may also have an option to do this.
However it may be easier to mask it with an iframe, however this will not be very good for SEO purposes.
To be honest I would prefer if you didn't do any masking, as leaving the Wikkii address in the URL will help to promote us a little bit