So, this is my second play through on the Xbox360 and at the point where I reach "Behold Shadowmere", I walk out of the Sanctuary and wait at the pool for him to appear. There are sound effects and the completion of the quest portion, but no Shadowmere. I reload. Still no horse. I fast travel and nothing happens. Is this a glitch and is there anything to do about this?

It's a glitch not just common to Xbox but I own the PS3 version and the exact same thing happened to me. Since noone else is chiming in I will give my 2 cents on this. I heard somewhere on the forums that you can sometimes start to experiemce glitches after your save file goes over 5,000KB...I believe it's graphical glitches which we seem to be experiencing.

I had a previous toon that joined the DB early, hence before the save file reached 5,000KB, and had no problems. I REALLY do not want to start over and believe all my save files are now over 5,000KB at this point. Can anyone please help? My only recourse is to ditch Shadowmere which makes me a sad panda

I joined the DB early in my xbox game but was way over 5,000kb by the time I got Shadowmere and had no issues, from everything I have read its one of those save and reload glitchs. I have heard it happens on the PC also but its a simple fix for us/me now.

Shadowmere died with my character, i fast traveled to a cave and when i appeared i saw a dead shadow mere fall from the heavens