(sorry about that! it's my first play-by-post combat!)

As the bats close in on Elbert, the Ranger strikes the creatures twice. His weapon slashes through the swarm of bats, but only manages to graze one or two of the flying creatures. They remain largely unharmed.

Carina attacks next, aiming her dark magic at the bats and bursting forth with her Eldritch Blast. However, although the Warlock's magic is sent straight through the swarm — the creatures that are hit take the brunt of the damage in stride.

The bats cluster together again after Carina's spell dissipates, flapping straight for Elbert. (Attack Roll: 6) Although the creatures swoop in close and try to nip at the Ranger's flesh, he swats them away with ease and they return to hovering five feet ahead of Elbert and Taiga — looking for who to strike next. Ragnus, it's your turn, with Taiga on deck. How will Ragnus react?

Ragnus will charge towards the swarm and move up next to Elbert. He will chuckle to himself as the rush of battle flows over him. He swings his battleaxe out in front of him at the swarm. 

Attack: 18 Damage: 6

Taiga’s hand shoots up defensively when the bats close in but they didn’t come for her. With the torch on the floor, she considers what would be best to use against the bats but she doesn’t have much options, so she draws her rapier and holds the shield a bit tighter. Surely, the rapier isn’t optimal against the small creatures but what can she do? Hesitantly, she lunges into the swarm and hopes to cut down a few of the small critters by mere chance.

Attack: 8, Damage: 5 mundane piercing 

(I just noticed that, when rolling in the forum, the roll D&D Beyond displays in the text and the actual result when you hover over the dice roll is sometimes different, like with Ragnus's attack roll ,,,, from this point on I'm gonna follow what the roll says when you hover over it, but also remember you can make rolls and checks straight from your character sheet too! sorry for any confusion guys, I didn't realize the forum messed it up)

Ragnus charges towards the swarm of bats with a chuckle. When the Dwarf swings his battleaxe, his violent hit sails through the flapping creatures and cuts down a number of the bats. A few of the winged creatures fall to the cavern floor, and the remaining bats in the cluster are heavily wounded. Taiga follows up, aiming with her rapier, but her weapon isn't able to strike any of the bats as they flap about.

Now it's Brix's turn, with Elbert on deck. What will Brix do?

(From my experience - and I did and still do a lot of rolls in the forum - the actually displayed number is more likely to be correct than the tooltip. Often you roll one dice with a modifier and both dice and modifier are wrong in the tooltip. On the other hand, the color of the roll shows special values, like red for a lowest roll and green for the highest, then, even with wrong tooltips the displayed number typically matches the theoretical values for the range of rolls. Therefore, I would always recommend to trust the displayed number and doubt the tooltips. That said the best way is to use the roller on the character sheet, because when you roll there and you’re in a campaign, then the roll will show up in a game log that everyone can see. From there you can simply copy the rolled number here.)

(OHH okay, thank you Cyreon! I was wondering where Ragnus's +11 came from, that makes a lot more sense. in that case, both Ragnus and Taiga missed their attacks, hehe. these bats are nimble, and still look largely unharmed. I apologize again for the confusion, guys!)

(No worries! Confused me too. Man these bats are tough...)

"BATS! I HATE BATS!" Squeals Brix as the bats begin to swarm around the party. He takes a vial from his bandolier and pours out a small bit of powded in the tiny palm of his hand. He draws in a big breath and using a magically infused exhale blows across his palm distributing the powder into the air.  Any BATS that don't make a Dex check are now outlined in purple faerie fire. He then drops to his knees and covers his head in an attempt to avoid the bats.

Elbert continues to swing at bats with both ends of his weapon.

Hit: 24 & 22

Damage: 4 & 4 (that would be four 1’s in a row if your counting, lol)

Keeping her shield up, Carina retreats further as her eyes strobe black once more with the dark beam of energy from her fingertips at the bats.

Eldritch Blast to hit:  24 (or 25 if at advantage from Brix's Faerie Fire, but a non-crit hit either way).
Eldritch Blast damage:  7 force damage

The swarm of bats, unable to avoid Brix's powdered spellcasting, are set aglow with Faerie Fire. Gleaming from the Artificer's magic, the flying creatures are attacked by Elbert next. They take the hits from the Ranger's glaive, finally beginning to look a bit worse for wear. And then, as Carina's magic shoots forth from the shadows and unleashes another Eldritch Blast at the swarm, many of the bats fall to the cavern floor. The remaining bats in the group shudder from the pain of the Warlock's dark magic, and use the opportunity to fly away to the other end of the cavern — heading for a tunnel in the darkness. You all gain 10 XP.

However, silence does not yet fall upon the dripping cave. The party of adventurers hear the sound of footsteps behind them — and the three bandits from the other end of Croaker Cave have followed the noises of combat, blocking the tunnel from which they came. One of the bandits, a wicked-looking Elf, narrows her eyes at your characters calculatingly. Then, she charges towards Carina. She takes a swing at the Warlock with her scimitar, but the weapon slices through the air beside Carina, clanging into the cavern floor. It's now Ragnus's turn, with Taiga on deck. What will Ragnus do?

Ragnus moves towards the bandits and takes a swing at the wicked- looking Elf, but his hand slips on some guano on his battleaxe and he completely misses (Nat 1). He yells at the bandits, "We're here ta help!"

Taiga moves to Carina in support against the bandit with her weapon drawn but does not attack yet. "Stop attacking us! We are here to speak with Hulil about a certain disease that killed already two, afflicts her sister and probably Hulil herself, too. We're here to help finding a cure for it as it threatens everyone's life in the region. On our way we were ambushed by these bats because we don't know the right way to Hulil. Would you bring us to her, or show us the way?" Taiga holds her attack, ready to strike at the elf at the first sign of aggression from the bandits. 

The bandits keep their weapons bared, and the Elven woman beside Carina lifts her scimitar again and growls under her breath. Another bandit, the Dwarven man, speaks up — glaring daggers at Taiga. "And why should we trust that you strangers are here to help Hulil? What's to say you aren't here to rob us?" he demands.

„We’re here to help fight the disease outbreak and Hulil is just one of too many victims. We have reason to believe that she brought the disease agent here into this cave.” Taiga argues, “heck, all of you may already carry the disease for all I know.” Taiga looks at the elf with these last words and takes a step back to bring distance between her and the elf as if to reduce risk of infection and paint an image of danger. “We’re in the process to identify the source and search for a cure. But I won’t lie to you, everyone infected until now simply got colder and colder until they froze to death.” She waits to let the words sink in and hopes that the bandits realize what a dire situation Hulil brought them into. Sheathing her rapier, she says, “Well, why don’t we let Hulil decide if we’re worth her limited time if she is already as advanced as her sister with the symptoms?"

Persuasion: 3 (advantage if someone helps: 13)

Carina sighs.  The bandits had gotten the jump on them just as she feared.  But in truth, this conversation was going to have to happen regardless.

She attempts to help Taiga's argument, bringing up a Minor Illusion of Tulgi, diseased blue veins and all.

"Who do you think sent us to this cave?  Not Elro Aldataur who now has custody of the five Hulil sent to raid Pelc's store once more."  (This is technically true - Elro did not send the party to Croakers' Cave, but Carina is implying that Tulgi sent them by her illusion without actually lying outright).

"When you've got a losing hand and everyone knows it, at some point, you have to stop betting.  Tulgi is dying.  And she knows Hulil is following in her footsteps.  We know the source of the disease is one of the artifacts that Hulil received from her sister.  The scroll case, the jade statuette, the quiver of arrows, the silver ring, the two blue glass vials.  No further burglaries are going to cure it.  Healers have failed.  We need magic to study these relics, properly quarantined, and find the cure before all of you and all of Uthodorn catch it.  You accuse us of wanting to rob you?  Of the very items you and Tulgi robbed from Pelc's?  At this point, our taking these items from you may be the only thing that prevents you from catching the Frigid Woe!"

Carina leaves it implicit from her Minor Illusion that the party is better suited to access the magic and arcane knowledge to find the cure than the bandits are (though she herself is far from sure whether they are).

Persuasion (or Deception or Intimidation, same +6 bonus, and a little of all three, really):  13

Brix peeks out through the crook of his arm. Seeing that the bats have retreated, he stands and brushes at his clothing removing any dust or debris picked up from the floor. With a dry chuckle he looks about sheepishly and says, "Uh, heh, uh...Bats. Uh...Yeah." 

As Taiga and Carina explain the circumstances that have led the party of adventurers to this point, including their goal to find a cure for Hulil's disease — the bandits listen, reluctantly lowering their weapons as they do. When the Warlock mentions that the group that'd been sent into Palebank Village was now in the custody of Elro Aldataur, the three of them grow angry again, distrust crossing their faces as they give your characters wary glares. But when Taiga and Carina are done speaking, the bandits realize they'd be fighting a losing battle, and carefully sheathe their weapons.

"Fine, we'll take you to Hulil," the Elven bandit growls, giving Carina a venomous stare before she turns and leads the way deeper into the cavern and into the darkness. "But don't try anything." She and the other two bandits lead the adventurers past the foul-smelling cavern and into another tunnel, which eventually emerges into a wide underground clearing. This appears to be where the bandits make camp, for there is a circle of bedrolls arranged around a cold fire pit with empty bottles strewn about. The bandits pass this area and head into yet another tunnel — a wider one, which leads to another large, dark pool of water. Cold droplets from the stalactites above fall to the cavern below, the sound of water echoing around a deep croak.

Slowly from the depths of the pool rises a wet, slimy creature — a giant ice toad larger than all the others so far. It stops at the edge of the pool, watching the bandits and the party of adventurers with large, gleaming black eyes. "Well," says the Elven woman, gesturing to the giant toad and stepping back, the hint of a smirk in her voice. "Get on."

Before leaving the scene of the fight, Carina would have grabbed a couple of the dead bats (as suggested by Taiga), and handed them to Elbert to work his Animal Handling magic.  At the time she would have intended it for the regular croakers, but now she hopes it will work on this larger one.

OOC:  Question for DM on XP.  I have only ever played using milestone-based level advancement in 5e.  For XP, do the characters only get XP if they fight as we did with the swarm of bats?  What about (relatively) successful negotiation as with the first couple croakers in the pool by the entrance, with the five bandits at Pelc's, and with Tulgi in her cabin?  Any XP for that?  If not, my worry is it sets up a meta-incentive for PCs to attack everything.

(in the case of adventures like these, which are meant to take the characters to a certain level if they manage to successfully complete the adventure, the XP is sort of a combination of the point- and the milestone-based, at least the way I'll be running it. your characters will get XP for defeating creatures in combat, but you'll also gain XP later on for story advancement and successful non-combat encounters too, don't worry!)