I lost him a while back, I have searched the world of Skyrim. I journeyed to Mordor and back to try and find him, though I cannot find him in the place from whence he came. Does anyone know how to fix the disappearing shadowmere? He is not dead, he just left.

It happened to me, too, as you remember. Not sure how to help... lost Shadowmeres! D:

He would have died somewhere and will respawn WHERE HE DIED. Check likely places otherwise use the console to tele to him if ur on pc.

He didn't die

How can u be sure thats the only reason for him not being there for not fast traveling.

Because I caught him when he was dead then got him back, I left him at the whiterun stables when I tried buying a new horse for my follower. Not long after that he left.

Hmm.... check the location where he died that time u got him back... indulge me.

Mhm the lose of shadowmere...

I allways found that horse a bit.... strange...

Lol, alright. Wouldn't hurt anything.

Sometimes I wonder if he is living a double life I don't know about.

or u could always check the place u got him the first time... he probably just walks back..

That may be the issue. I've been told that we can own multiple horses and they return to their stable of origin when you take one of your others. IDK how the game decides which horse goes with you when you Fast Travel, but with all the various bugs I'm betting the game doesn't handle this very well. I guess you've checked the eery pool from which he originally rises?