4 Horsemen of the Fantasy Apocalypse

So your planning a fantasy campaign and want to have something grand going on in the background. Perhaps to include a prophesy and you decide to do "The 4 Fantasy Horsemen of the Apocalypse". Unicorn and Pegasus come to mind as well as hippogriff and nightmare mounts. The hippogriff is perhaps not a good mount. But it could also could be the 4 riders of the storm and one of them could be a wyvern.