"Odyssey" was a code name for a Windows release. Windows Odyssey was going to be released alongside Windows Neptune which instead of being a home release like another project called Neptune, it was going to be another release for business users based on the NT kernel.
A few month(s) after the development of both Windows Odyssey and Windows Neptune and the project got actually cancelled alongside Windows Neptune which also got cancelled and the two development teams of both Windows Odyssey and Windows Neptune were merged together to create a single operating system which was called Windows Whistler that had edition(s) instead of separate releases which were the Professional and Home variant.
See the Windows Neptune page for more information about the post-cancellation.
There are no confirmed builds under the code name of "Odyssey".