User blog comment:AwesomeDaxter/What do i do next??/@comment-4720239-20120105210544/@comment-4674838-20120105213255

If you're high enough so that harpies are spawning, then the Wyvern should spawn there too. The height differs depending on world size and stuff. By the way if you didn't know, I thought I'd point out that I just made a Wyvern walkthrough yesterday.