Consider the D&D Frogs

Dunno why the jumping one has a rack, but finding wide bullywug pics is hard.

Frogs in D&D worlds get a bad reputation. This is little surprise when one considers that so many unpleasant species - froghemoths, slaad, bullywugs, grung, and banderhobbs - have amphibian forms and origins. I wanted to have a go at adding some details to the last three on that list, connecting them together and giving them some differentiation from my takes on other low-level enemies, such as kobolds and orcs.

Bullywugs

These are the bread and butter of frogfolk. Grung and banderhobbs are merely variations or developments of the original bullywug template. They are 4-5 feet in height (females are larger than males), varying in mottled tones of green, grey, and brown. They sense the world primarily through sight, but in the water their sense of taste and touch is amplified; the water becomes akin to an extension of their skin.

Bullywugs live in wet environments out of necessity. Their skin must be regularly moistened to enable them to breathe properly. This puts a limit on their range and resources, but has made them masters of this domain (at least until something more powerful comes along). Bullywugs that engage in trips outside of their wet domains have found various ways of dealing with their water dependency- carrying multiple waterskins, sticking to riverine communities, or forming pacts with water elementals are just a few options available.

Bullywug technology consists of animal usage and repurposing of natural resources. Food is gathered through wormeries and fisheries, or hunted with spears and nets (food is consumed whole- frogfolk cannot chew). Their clothes are purely practical, made of reeds and grasses and shells. Armour is harvested from oyster reefs, weapons from animal teeth and bones.

More resourceful individuals turn the wildlife around them into weapons: venomous snakes on sticks, bags of leeches and mosquitoes, crayfish on leashes, caged snapping turtles, dart frog familiars. All bullywugs can speak the tongue of the dire frogs, which they can coerce into acting as mounts. Smaller frogs constantly fill the air with reverberating calls, a spy network only accessible to those who can decipher their croaks.

The politics of frogfolk is rarely fair. Typically they resort to plutocracy or kratocracy, where the largest and most forceful individuals gain power. To rise in such a government, one must flatter and wait until the opportunity comes to ascend, or forcefully take the position for yourself.

Poison is the common tool of the trade for usurpers. Bullywug skin openly absorbs water, and a sufficiently diluted toxin can enter their systems with little more than a carefully planned handshake or spiking a favoured swimming pool. Outsiders that learn of this are quickly silenced, for a larger scale deployment of this method would be deadly for bullywugs.

Frogmen by Jamie Jones

Bullywugs can come into conflict with other humanoids for various reasons: uncontrolled exploitation of natural resources (peat in particular comes to mind), overhunting of wildlife or collecting of alchemically important plants, and the general initial hostility of other races can all lead bullywugs and their kin to lash out at humanoids and their settlements.

When they go on raids, they do not do so through frontal assaults. They prefer to sneak and squirm their way into houses and caravans. They swim up creaks, into canals and cisterns, through sewer passageways. Their calling cards of damp footprints and bog stench is well known, and narrowing down where they came from will not take adventurers much time; as such, bullywugs only do this if they feel confident that they will have the upper hand in any retaliation.

The frogfolk take food, hostages, and gold. They have little need for ferrous metals, and no use for tools that require resources they do not regularly come by. Gold however is highly prized, for it will remain in relatively good condition in their swampy homelands. Favoured hostages are those who won't fight back and those who can be made useful to the tribe. Tool makers, scholars, and mages are forced to share their crafts and secrets, allowing the bullywugs a slim chance of advancing beyond their current state.

Grung

Grung are smaller cousins of bullywugs, having adapted to life in tropical rainforests and jungles. They have formed mutualistic relationships with toxic insects, providing them with protection from various predators/entomologists in return for the sole right to eat them. The consumption of these invertebrates grants them access to incredibly potent toxins that change their skin colour and make skin contact with them dangerous.

Over time, the discovery of different potencies and effects has resulted in various class and caste-based societies forming, focused on isolating insect breeds and restricting access to them to specific groups within a tribe. In some tribes, this nature is clouded through druidic magic and tradition as being the result of a higher calling: in the eyes of these tribes, the grung are destined to fulfil a role in the tribe, and this role is marked on their skin for all to see and judge them by.

Grung dwellings can be quite beautiful, filled with pool-collecting plants (used as tadpole nurseries), brightly coloured frogs, and high tree canopies. Few see these places under favourable conditions, for the grung are known to capture larger humanoids to use as slaves, acting as manual labour or interacting with creatures that the grung do not wish to poison. These slaves are kept under threat of death by poison, swarming insects, or physical violence (grung have small teeth, similar to some bullfrog species).

In certain regions, bullywugs and grung can find themselves in the same territory, distributing it between the treetops and the waters below. On rare occasions, alliances and interbreeding occur.

Banderhobbs

A banderhobb is the spawn of the same batrachian entity that steered the frogfolk into being. Through a ritual of bullywug blood, a dire toad's skull, and necromancy, a banderhobb can be brought into the material world. They look like bear-sized toads, for the most part.

(yep... definitely just a regular toad)
art by Christian Müller

Banderhobbs are created as assassins and collectors, sent to take hostages, silence enemies, or cause general chaos for their masters. They can swim through shadows as easily as a salmon can swim up a stream. They move silently and with stealth unexpected for creatures so big. When they find their target of choice, they swallow them whole, taking them into a hole of darkness.

Being in the stomach of a banderhobb is maddening for any extended period of time. There is no ability to feel or perceive within its stomach, like being trapped in a dead body.

art by Dawid Jurek

Banderhobbs typically dissipate once their duty is done. Some however may remain, kept in tact through necromantic bindings and offerings of flesh and blood. These banderhobbs can learn to harness the shadows and silence even further, able to bend it to their will to better serve their masters, or break their chains and seek out their own paths in life.

Banderhobbs can understand the speech of frogfolk, but they cannot speak in return. Their meetings are typically brief, and alliances uneasy. It's hard to be friends with something made from the head of a severed pet and the blood of your tribesmen, even if it looks like a shadow frog.

Sources:
Bullywugs can be found in the Monster Manual, pg 35
Banderhobbs can be found in Volo's Guide to Monsters, pg 122
Grung can be found in Volo's Guide to Monsters, pg 156-157