User blog comment:Vivaporius/Extra-Galactic Invasion Campaign Idea/@comment-25027290-20120706182659

Like i stated in the chat: The Sanguinites may fit into this somehow.

-They are an advanced Xeno race that was "wiped-out" by the Eldar long before the collapse of the Eldar Empire

-They have no connection to or ability to use the Warp

-They may have been created by the Old Ones

Now i think you may be able to tweak them a bit to fit your preference if you so choose. Anyways that is my recommendation if you cant think of something better