So yeah I was doing that killing Guardians quest, and i lost my shadowmere at the guardian Sabre Cat area, BUT... I can't relocate that area! Anyone could send me a screenshot of the area it spawns at again ? I've been wandering that area but haven't found the exact spot... using my detect life spell to find her too but so far no luck!

I have no idea, but once Shadowmere dies he's gone forever. So lets hope he's not inside the Guardian Sabre Cat's belly.

He's suppose to appear next to you when you fast travel so chances are if he doesn't, he's gone.

Well I finally found my Shadowmere again, took me 3 hrs but it was at the Sabrecats location ! lol Just standing there, and lookin' around. All thanks to Aura Whisper, i saw her through a huge mountain that I was sure I had checked out