Well, three of them are Goblins, so you'll take what small mercies you can

Goblin Looter... sounds like a basic scavenger, really. Not the most effective combatant. The Overseer might be more of an issue. Though, admittedly, they're all alive, which means that your Shadow Wave will be less useful then you'd like. You sigh, and stand before heading down the stairs as quietly as you can. You want what information you can get, so eavesdropping sounds like a good idea.

"Hey, Boss," a high-pitched voice starts. "Youz sure this a good idea? Oi mean, all dem shadowy-boyz..."

"Stuff it, weedy," A much deeper voice rumbles. Almost certainly the orc. "Da warchief says to loot the tower 'cause that sneeky git says he saw two adventurers go in, stay the night an' come back out. Means no more shady-dead for a bit, it does!"

"Ya, dat makes sense, but... It feelz... wrong. Like walkin' into a lone wolves den, only t' find out it's one o' those rock-bearz..." A third voice speaks up, nearly as high pitched as the first.

You've heard two goblins and an orc so far, so that leaves one goblin unaccounted for. You finish descending the stairs and come face to face with the third.

Level 1 Goblin Looter, Monster, Goblin, Goblinoid

You're both surprised to see the other, but the goblin is FAR moreso- you, at least, knew they were there, and thus recover first. You drive the base of your staff into the goblins' gut, forcing it back and depleting most of its health bar. Leaving the doorway, you bring your staff around as hard as you can as the goblin tries to turn to the side, scrabbling for the dagger at its side. A pointless gesture, as your blow impacts its chest, finishing it off. You wince briefly at the crunch of breaking ribs, then keep going. One down, three to go. Reaching the door to the main room of the first floor, you begin charging a Venom Dart right as the others start reacting.

"Oy, wat was tha...." The orc turns to the door, and his face slowly morphs into a picture of shock, giving you the perfect opportunity to peg him with your spell. Your acid-green dart sinks into his chest and he bellows. "Kill th' Human!"

Their numbers might make things tricky, especially given their resistance to your only AoE, but you're a both a much higher level then them, and have back up. The Bat you had stay behind zips in the open door and sinks its fangs into the orcs' arm and twists, before releasing and shooting up to the ceiling. The orc bellows again and takes a swing with it's crude broadsword, which misses your agile little skirmisher handily. The goblins look between you, trying to decide what to do, and you decide to refocus their attention on you, charging up a chill ray and unleashing it upon one of the goblins. They stagger, their green skin turning a frostbitten black, then keel over. Okay, you'd been reasonably certain your skill with that spell wasn't enough to kill them, even accounting for the level difference, so whats... Of course! Your new staff. Taking it as your boss drop is absolutely paying off.

The orc snarls when the goblin hits the ground, making a snap decision. "You deal wit' the flying mouse, I'll kill the pinkskin!" he barks at the remaining goblin, and starts charging at you. A startled squeak indicates that the goblin HAD managed to nick your Bat, but you had more important matters to deal with.

You only manage a single cast before they're on you, forcing you to deflect the broadsword and step back for additional room to maneuver. Taking the bait, the orc snarls and steps forwards into the doorway, where you promptly snake your staff between his feet and twist, sending him falling to the ground. Unlike with Ser Jhondoe the Paladin, where you had admittedly been hoping he'd grow a brain and stop attacking you, you don't give the orc time to stand, driving the tip of your staff into his throat. They ****, gurgling and try to grab the doorway to pull themselves upright, only to stiffen and collapse as your Venom Bolt does it's job.

The melee in the main room is going very slightly in favor of your Bat- the final goblin is covered in streaks of blood from its' slashing attacks, and while the skirmish isn't going all its' way, each wound it inflicts heals its' own. In an honestly surprising display of acrobatics, the Bat slips around the goblins' dagger and sinks it's fangs into their throat, causing the goblin to drop their dagger and try and grab the Bat. A futile gesture, as your Bat drains the last of the goblin's life before their hands can close. A glance at your Bats' health indicates the fight was enough for it to level up.

Level 2 Vampire Bat, Monster, Bat, Blood Bat

You're not sure how close the actual fight was, thanks to the level up restoring your Bats' health, but it won, and you now have four corpses. You shrug, thank the bat, and get to work.