"...a tiny creature entombed in the bowels of a planet."

The fourth time Leigh Brackett took us to Mercury was in the novella "Shannach--the Last."  (Published in the November 1952 issue of Planet Stories.) And as that tale begins, we discover that a prospector named

Trevor is having a really bad day.

Trevor has been flitting around Mercury's Twilight area for years in his small ship, hoping to strike it rich by finding at least one sun-stone--a valuable radioactive mineral that exists only on our innermost planet. But his luck has turned bad--a quake "brought down a whole mountain wall on his ship, leaving him with a pocket torch, a handful of food tablets, a canteen of water, and the scant clothing he stood in."

The Twilight area is made up of self-contained valleys surrounded by mountains that climb up over the edge of the thin atmosphere. So climbing out isn't an option. Instead, Trevor finds a cave entrance and blindly hopes to find his way through pitch-dark tunnels.

He's exhausted and dehydrated by the time he does find an exit into another valley, but there's no chance to rest. Because this second valley is inhabited and many of the inhabitants are rather nasty.

The situation is thus: three centuries earlier, a ship crashed in the valley. Most of the surviving passengers were colonists. But a number of them were convicts--at the time, convicts were sent to Mercury to help work the mines. Soon, the convicts (now known as Korins) were enslaving the colonists. The Korins used flying creatures to help track and attack escaped slaves. Both the Korins and the flyers (called "hawks" though they are more reptile than bird) wear sun-stones on their foreheads, which apparently allow the humans to stay in telepathic contact with the hawks.

Trevor falls in with an escaping woman slave and they join a larger band of escapees. But though Trevor sympathizes with the slaves, he simply wants to get his hands on a priceless sun-stone and get away. But his attempt to do this leads to the discovery of an alien creature named Shannach.

And that's all I'm going to tell you--because this is the sort of story that needs to unfold for you while you are reading it, without any spoilers getting in the way. It's available online HERE.

All I can say without ruining it is that Shannach is an imaginative and unique creation--a creature with perhaps a hint of Lovecraftian horror to him that makes him an effective villain and and throws Trevor into very intense battle of wits, willpower and courage. It is, I think, my favorite of the four Mercury stories and one of my favorite Leigh Brackett stories of all.

That finishes up our tour of Mercury as told by Leigh Brackett. Of course, she took us to Venus, Mars and a few of the outer planets as well, so though this is the end of this particular series of posts, there's every chance we'll return to the Brackett Solar System in the future.