Salamander

Nine color variants exist and they behave identically, so which one you meet changes nothing. It does not chase. Once it has a clear line to you it roots in place and spits acid along that line, which means the danger is standing still in a cavern corridor while it works. Break the sightline or close the distance, because strafing at range just hands it free shots. Most hits carry Poisoned and the duration stretches with world difficulty, so an Expert or Master run wants an antidote or a regeneration source rather than eating the ticks.

Which cavern creatures your world can produce is settled at world creation. This one, the Crawdad and the Giant Shelly form a set of three, and every world gets two of them, never all three. If you keep meeting crawdads and shellies, your world has no salamanders and no amount of farming will change it. The game accounts for that: the absent one unlocks in the bestiary once you have the other two, and its banner can be built out of any two banners from the group.