Makiri

Makiri is a very tiny celestial object which orbits Liabo, regarded as a moon by astronomers on the surface of Elanith. It would not be widely recognized among laymen, who cannot see it with their own eyes. The Tehir tribes do not acknowledge its existence. While irregularly shaped and dark, the surface is oddly smooth. Though the superstitious believe it has become much larger over time, more reasonable people think this can be explained with orbital precession or even observational refinements.

Reference

• The Elanthian Moons

Behind The Scenes

Makiri was destroyed in a cataclysm prior to the setting of DragonRealms, which is set thousands of years in the future on a continent far away. Within the game it is explained that Makiri is some kind of egg, which hatches as a "world dragon." The world dragon scorches Liabo, and battles with the "Immortals." Shards of Makiri smash into the surface of Elanthia, causing tsunamis and catastrophic damage. These are, of course, oral traditions. Whatever actually happened is unknown. There is a mural in Shadow Valley that can be interpreted as a prophetic vision of the razing of the world.

Shadow Valley was designed around the time DragonRealms was released. It has a very subtle theme of temporal distortions and visions across times, where a prophetic vision of the world dragon would not be out of bounds. The valley itself may be an homage to the "Visions" of Andraax, along with the story of The Broken Lands, which would originally have been near each other and represented The Unlife as a shadowy serpent. More naively, the symbol refers to the sleeping Terrorite demon of Shadow Valley, which was essentially a large serpent with wings. There are other subtle moon themes in the story, such as Selias meaning "moons" in Greek, and specific allusions to other stories. Similar motifs with transient spaces and the moons were explicitly revived much later in the Red Forest.

[Mine Tunnels]
Swirling blue symbols formed of luminescent moss mark the walls. Though none are of any symbol set you can recognize, the largest is quite obviously a dragon.  Several spheroid-shaped patches of moss surround it, causing the entire wall to be reminiscent of a star-covered night sky.
Obvious exits: southeast

>glance symbol
You glance at a large mossy symbol.
>look symbol
The symbol is shaped in the form of a large dragon, wings extended and breathing fire upon a small planet just underneath it. 

Swirling spiral symbols were common in ancient Celtic burial mounds, which is relevant to the specific Lovecraftian background of Shadow Valley. The world dragon of DragonRealms is sleeping. The use of the word "dragon" in Shadow Valley is loose, actually referring a "wyrm"-like demon. It would be reasonable to guess the "world dragon" was extra-planar in origin rather than literally a "Drake".