Lunar Blaze Chapter 10

Hello Comments in bold. Mind you, I haven't read the other chapters, so I might be focusing more on style than theme/plot itself, but I'll do my best

In horror stories, scary monsters jumping out of the dark isn’t far from the truth. Revise this... in horror stories they are the truth, they are the norm... the sentence sounds rather awkward anyway,structure wise. Rephrase.
The next terrible moment there was a gurgled cry and a figure came flying through unknown towards them. Rephrase that too, wounds awkward. For instance, this would read better: The next moment was terrible, as with a gurgled cry a figure came flying towards them through the terrifying unknown they were surrounded by. Or something. It reflected the light from Selina’s ring and sent golden streaks slashing across the stone walls.

And then Jimmy and Stheno toppled to the floor.

As it seemed, Stheno had once again found her prey, and was on top of Jimmy, pinning down his arms and legs and about to rip out his spinal cord. Acting fast, Selina charged into Stheno, and found it was like charging into a statue. Reconsider the second "charging", avoid repetition

Yet, miraculously, Stheno was forced off Jimmy. She crashed to the ground, sending dirt and rocks flying from the impact. Selina scrambled to her feet, just as Stheno rose like a mountain of monstrosity. She swiped her claws, and Selina ducked. Where she had been, Stheno left a ragged trail of scratches in the rock. A bit too much like telling, not showing. Maybe zoom in more on their features, eyes, what sounds they might be making - it will bring this scene to life

“Run!” Jimmy yelled, and Selina began to sprint. Jimmy followed close behind, practically stepping on her heels. And then there was Stheno, what looked like an angry, giant piece of gold bounding after them causing an earthquake because generally she was a very heavy snake lady. Rewrite this last sentence. The narrator's tone suddenly changes from neutral to humorous (what with the 'causing an earthquake', 'very heavy snake lady'. Too reminiscent of Lemony Snicket), skipping between the two will make reading difficult for the reader. Pick one and stick to it.

Of course, with the uncomfortably high temperature and the fact that they were running for their livescomma it wouldn’t have been a surprise if they had flooded the caves with sweat.

The cave walls became narrow and both Selina and Jimmy had to duck to avoid scraping their heads. They even Cut the "even", redundant, and it just sounds (well, reads) terribly, as if you're missing adequate words to get your meaning across - you want to strongest words to paint the most vivid pictures had to turn sideways and act like crabs. Yet for Stheno, it wasn’t as easy as squatting down and looking like a retard. She hit the walls multiple times and sent sparks cascading off the walls Repetition and grinding stone echoed. This sentence doesn't make sense

Once she became stuck, only to shove herself out of the small space with a roar of anger. It seemed that Stheno had endless energy, which may have been since she didn’t even breatheReads awkwardly, as if you missed a word... . Soon they would run out of energy Repetition, too tired to run.

The tunnel now wider, Stheno began to catch up. Her brass fingers scratching at Jimmy’s green dark blue jacket as it trailed behind him like a cape.

It was then that luck turned. A ledge that twisted around the edge of a rocky cavern, below was a pit of demons sleeping in the shadows. Stheno grabbed Jimmy’s jacket, yanking him backwards he toppled to the ground and groaning at the impactRewrite this sentence, your tenses are a complete mess. Selina skidded to a halt, and spun gulping as small rocks rolled over the ledge and streamed down to the piled predators.

With Stheno standing an inch away from ‘certain doom’ Selina ran and pushed her hands into Stheno’s "his", repetition of names chest. Stheno wobbled, and like a stone, she dropped. Selina doubted that the demons would have been able to rip Stheno apart, but they definitely would have been able to rip her apart. As she threw her arms around like a maniac, and her fate had been decided, she realized it was probably the weirdest way to die. For one thing, she’d die twice. The demons would rip her apart and she’d die, and then they’d eat her soul and she’d die again. And that was it, gone. How is this dying twice - in other words, what exactly is the definition of death here? make that clear

It was kind of funny in a way, but she didn’t laugh, Semi-colon even though everything was happening in slow motion there was no time to laugh. The closest thing to a laugh that came out of her mouth was a shrivelled up shriek of sudden realisation. Hello death.

And then a hand grabbed her clothes and another her shoulder and she was whipped back onto the ledge and into Jimmy’s arms like a yoyo. She sagged, relieved, she let out a sigh and wiped her forehead.

“You’ve saved my life again Jimmy, I owe you.”

“You do,” Jimmy grinned, and then peered over at the angry demons that were swarming Stheno.

“They’re not going to stop her commaare they?” Selina inquired.

“Nup is that even a word?,” Jimmy mumbled, “just make her even more pissed at us.”

“Fantastic,” She said sarcastically.

“Moving on,” Jimmy said, spinning on his heal spelling and pacing towards their destination, wherever that was. Selina followed, flinching each time Stheno let out an angry shout. It almost made her laugh.

You seem to have a tendency to avoid explicitly saying what's going on - as if you avoid saying "there is/was" and just throw in the images, which makes understanding what;s going on rather difficult. Make sure your writing flows and is easily accessible for the reader, nobody will want to plough through unclear prose to try and figure out what you might be trying to convey.

Proof-read your work before posting because you have loads of small mistakes that distract from what you're saying - messy tenses, spelling grammar.

Perhaps try reading your work aloud, maybe that will help you see what's unclear, what needs to be changed to read more freely.

Also, more character development - it's not bad as it is but more needed. I liked the chapter generally, but it does need more work and fine tuning. Read some more fast-paced books to get a feel of the language, fragmented sentences, all the mechanisms used to increase the effect of speed, action, fast-paced events.

Good luck with it! Let me know if you need anything else

~Ink