Shadowmere is the only horse in Skyrim that can't be killed. He will die ridden off a cliff though (but "resurrect" comes in handy )
I painted this one, as usual, in ArtRage (best painting program out there, not expensive either - little plug, no I don't work for them!). I can't remember but I'm pretty sure I would've done this in oils, plus sticker presets for the grass and bushes.
I'm a total Skyrim fanatic, addicted for sure. Thanks for looking guys