For a scenic browse, and an answer-page for Guess The World...
...Luminous insects swarmed around them, and moon-pigs coughed and grunted nearby. They were following a vague Greenie path that ran westward. Whitey stopped suddenly to detour carefully around a rotted trunk, upon the side of which hung two things like bulging white pods.
"Blood-fungi," grated the old man to Crane. "Don't touch 'em - they're the most horrible way you can die, if you break one."
Then Whitey raised his voice in an echoing call.
"Kruppa! Where the devil are you?"
Crane sensed something tense, foreboding, about this darkening jungle. Or was it just that his nerves were harp-string taut?
"Kruppa!" yelled Whitey again. This time came a distant answer.
They pressed forward, and entered a little glade in the jungle... A huge, grotesque object towered at its center, and Kruppa was coming toward them from that point.
"What the devil are you doing here, fooling around the Greenies' god?" Whitey demanded of the Venusian...
Edmond Hamilton, The Revolt on the Tenth World (Amazing Stories, November 1940)
Stepping out, my nostrils were greeted by a most foul stench. The air was thick, heavy, warm, and very bad of odour. It was barely breathable, and an excessive heat poured up from the ground itself, which soon sapped my energy very much.
As soon as I set out to walk about, my feet sunk into the soil and it was necessary to keep pulling them out, which was accompanied by a most discomforting sucking noise. The ground seemed more like some of the semi-liquids that our scientists produce in their laboratories when they get temperatures high enough to almost melt ice!
For awhile I squshed my way along. Then a section of the ground before me swelled while I watched into a large hemispherical dome and snapped. A cloud of noxious vapour was released and swirled past me. It was most peculiarly like a bubble.
Coining upon a large pitted yellowish rock, towering isolated out of the ground, I stopped and examined it. It was composed of some porous hard shiny substance unlike anything nature produces. There was a most unnatural feeling about the thing.
There was a movement behind me and turning I saw one of the beings native to Umbriel. Oozing from a hole in the ground, came a large shapeless white object having neither arms, legs, eyes, ears, nor other external appendages. It had a mouth and a tubular several foot long slimy body.
Donald A Wollheim, Umbriel (Fanciful Tales of Time and Space, Fall, 1936)
>> Guess The World - Fourth Series
Comment from contributor Lone Wolf:
A very short story (announced as "short short story" - it is actually so short, that this excerpt is almost half of the whole text!), presented as "condensation of the report" of the Oberonian explorer K'yaldiu, explaining why Umbriel was a forbidden moon - it turns out, that it was a dead body of a giant creature, inside of which some nasty life forms have developed, although they are only alluded and not described, neither is made clear why they are considered so dangerous, that it shouldn't be allowed that they learn of the existence of the external universe. Perhaps the author just wanted to create a kind of horror aura around this moon because of its ominous-sounding name (from Latin umbra - "shadow"), which otherwise has no prototype in mythology or literature like the others (it seems that this is the only planet with a purely invented name and maybe because of that it is not very popular and there aren't much stories written about it).
Note from Zendexor: Most of the Uranian moons have been given Shakespearian names, but "Umbriel" comes from Alexander Pope. The reason for the exception is not known to me; perhaps there's an interesting story behind it.