A Welkynd stone, probably? The zombie also looks to be from Oblivion. The longer I stare at this, the more details I notice! Just art of yours depicting one individual is enough to keep someone preoccupied with admiring it.
That ghoul or skeleton in the background looks like a recent kill, it looks like the two adventurers just had a random encounter. I couldn't help but notice that glowing crystal. It seems to be the sole source of light in that tunnel. Looks like it was probably loot they picked up from the ghoul, or it's some sort of a map or lantern for navigating through the dungeon.