The dungeon ecologist druid would be insufferable in the sewer level. You're just trying to concentrate on breathing through your mouth and keeping your spell components unbefouled, and all the while...

"You know, it's a common misconception that otyughs are inherently hostile. They're territorial, but they'll back down once they sense that their nest isn't threatened. It takes a lot of energy for an otyugh to move around, actually. They prefer picking a spot with plentiful sewage flow and would ideally remain inanimate their entire lives."

"It's weird that we've been seeing so many vargouilles down here. They're infernal creatures, yeah, but they're opportunistic parasitoids and they don't survive well outside of the hellish ecology. Without a constant source of humanoid bodies to kiss, a colony typically dies out within a few weeks. Wonder if the Thieves' Guild has been dumping corpses down here again."

"Oh, hey, don't let your crawling hand familiar back on your shoulder just yet. He's caught rot grubs, I'd say about ten minutes back. Fascinating creatures, really. They're harmless to the undead, but once they sense body heat, they instinctually burrow towards a heartbeat. Just get him to stand still for a minute while I heat up this dagger. You know that most reports of zombification passing through bites are actually mislabeled rot grub infestations?"

"Oh, haha, yeah, don't mind the dire rats, just keep moving. We're in their house right now, they just want to know that we're not moving in. Did you know that there averages seven rats for every person in any given city? Just think: Ten feet under any street it's just solid rats. It's a credit to the Sanitation Guild that they don't come up the privy more often, really."

"A cave fisher! That's a rare one for this environment. They're Underdark creatures - they usually don't like environments with as much noise and flowing water as this. This little guy must be so confused, either that or most of the way to deaf. Try not to snap the filament when you wriggle free. Poor little guy is probably hunting by sense of touch alone."

"You know, you'd be surprised how much cultists contribute to the local ecology. Having a reliable source of heat and light, like devotional candles, can provide crucial energy to the lower level flora which are the backbone of the entire ecosystem. It's easy to think of the cultist as an invasive species, but they're part of the nutrient exchange between the sewer and the surface world. Oh, don't worry about killing them, a den is rarely left uninhabited for long. Look, you can still see the old hate-sigils of the Ravening Darkness! The cycle of nature is a beautiful thing."

"Ooh, that's a carrion crawler! Hold still, I... Ah, guess you don't have much of a choice in the matter. But look on her underside. She's carrying eggs! And quite a large crop of them, at that. These guys are scavengers, actually, they rarely actively hunt, but once those eggs hatch they're going to consume her for nutrients, so she's under a real evolutionary pressure to bulk up as much as she can right now. Once you regain use of your arms, try to aim away from the thorax. The eggs will do just fine if she's already dead a little."