Monster Monday - Grung Wildling https://www.dndbeyond.com/monsters/grung-wildling
The grungs are froglike people that live in the swamps of Chult and first showed up in the rules supplement Volo’s Guide to Monsters and the adventure Tomb of Annihilation.
The Wildlings are the scholar and caster caste of grung tribes, and they have red skin. There’s a curiosity with the stat blocks for these creatures: Grung Wildlings are considered 9th level spellcasters, but they only have up to 3rd level spells, 27 HP, a modest armor class, and a CR1. This is because Wildlings use the Ranger class table for their spells, and rangers get spells more slowly and have a smaller pool than many other casters.
Because grungs are a bit of an oddity, they lend themselves to being reskinned for other campaigns. For instance, you can build an entire new race of creatures with different castes and abilities, and you can plug each caste into the stat block for a grung. Imagine a race of insectoids or extra-planar creatures. Then you can just swap out the poison for another type of damage (as appropriate) and swap out the need for immersion in water for something else. If they are a bunch of living rock people, for instance, then perhaps they have to spend an hour merged into a stone like a boulder or bedrock or something to avoid the exhaustion.