Some good things, some things could use some work. Some of the wording and phrasing seems a bit awkward or otherwise problematic. The atmospheric electrical discharge is spelled "lightning". There are also some tense inconsistencies. Do you have an editor you can go over it with? As for the story itself, in medias res can work well, but readers need enough context to make sense of what's going on. Your choice of an apparently original fantasy world as a setting makes this more difficult because pretty much anything goes (potentially) until you inform readers otherwise. It's important to let readers fill in a lot of the details in their visualization of the story, but to do that, you need to sketch the basic outlines in first. So the first scene is in a dark and stormy forest. What kind of forest is it (e.g. young tangled growth, old growth with an open understory and fallen logs, conifer forest, palm grove, bamboo thicket, freshwater swamp, mangrove swamp, redwood forest, tropical rainforest, temperate rainforest, a single large banyan tree) and how is everyone placed within it (in the open, behind a tree or log, obscured by brush, distances and directions, relation to meaningful points of reference)? It's raining on the combatants, but how heavy is the rain (drizzle, moderate, downpour), and is it falling directly on them or working its way through the canopy? Is the darkness due to night, stormclouds, the forest canopy, or a combination, and just how hard is it to see? Without lightning, it's bright enough to fight effectively and to take aim at some distance, but it's not bright enough to see the archer or the two enemy swordmice at that distance?
A big thing that's unclear at this point is the degree of anthropomorphization
of the mice and rats.* They apparently have opposable thumbs set on humanoid hands, arms, and shoulders, and are capable of grasping things behind their backs and of walking upright. They make clothing and wear it similarly to how humans do (the use of tunics suggests a European fashion sense that might fit somewhere in the last two and a half millennia, which covers too much territory
to let readers know what kind of clothing they are actually wearing), build at least some structures, and know some metallurgy. The use of a bow and arrow and the swinging of swords suggests that they are closer to human scale than real-world mice and rats (scaling factors make momentum-based attacks less capable of inflicting damage at smaller scales, where stabbing and grappling would be more important, especially if armor is involved). They seem to be semi-monogamous k-strategists (like humans) rather than promiscuous r-strategists (like most small rodents). So far, for practical purposes the characters seem to be humans at some level of development from the Bronze Age to the Renaissance. But I don't know if I can trust all these inferences to build my understanding of the story's world because you haven't given much solid information about what model you're using for the characters and their society. Is it meaningful for the story that the characters are mice and rats, and if so, how mouslike / ratlike are they? What is the state of species relations (the mice working for Voltragen were described as traitors)? Does their nominal non-humanity have any effect on their motivations, or should we think of them as just humans with buck teeth and tails? As a reference in this regard, have you ever read Watership Down
A lot of this information wouldn't be hard to work into the two chapters you have up without disrupting the flow (it can even be used for characterization), and it would go a long way to making characters' motivations and the course of the story understood. You're doing fine on your choice of scenes and overall action. You seem to be going for an action-heavy, exciting story, but the lack of context makes that less vivid than it could be. What does Corvin actually see
, and think
? Depending on the level of anthropomorphization and level of visceral immersion you want, you might consider some smell and taste too. Emphasizing perception and sensory experience can draw interest to the action and to some extent make up for weaknesses that would break immersion or willing suspension of disbelief*. The slower-paced, solitary parts of the second chapter would be a good place to put some backstory as Corvin thinks about how he got there and where he's going.
*Looking through the DA comments, I see that you're going for a Redwall style of anthropomorphism. Which is fine, but I couldn't tell that from the story itself.
**The weapon physics was only an issue for me because I was in a position of trying to figure out what was going on with inferences based on details that can usually be glossed over. If you make it clear that the characters are at a certain scale, most readers won't be looking for clues and then stumble across a break from reality that is usually excusable and easily overlooked.