Giant Frog

A friendly giant frog is a witch's sentinel, a bullywug peace offering, a swamp druid's wild shape, or a memorable result of a Speak with Animals conversation that went somewhere unexpected. The frog does not understand strategy, but it understands the territory. Run it as a guide and a swimmer, not a fighter.

In water, the frog is genuinely useful. It can carry a Small character on its back at a 30 ft. swim, drag a rope to the far bank, or scout the bottom of a flooded crypt with Darkvision 30 ft. Stealth plus 4 from the waterline means it can creep up on a bullywug camp and come back with a head count. Out of water it walks 30 ft. on land but is conspicuous and clumsy, so keep it in the bog for any meaningful task.

Combat use is limited. If the players push, Bite at plus 3 for 1d6+2 piercing works. The frog has 18 HP and AC 11; one hit from anything serious puts it down, and the party should feel that fragility. Have the frog answer to one specific cue: a whistle, a name, the smell of particular bait. When the cue is gone, the frog wanders off to find food. Ally beasts work better when their loyalty has a clear off-switch the players can mourn losing.

A giant frog is an ambush from the waterline, almost never a single combatant. CR 1/4, 18 HP, AC 11, walk and swim both 30 ft., Stealth plus 4, passive 12. Bite is plus 3 for 1d6+2 piercing, and if the target is Medium or smaller it gains Grappled (escape DC 11). Swallow ingests a grappled Small or smaller target, dealing 2d4 acid damage at the end of the frog's next turn.

The giant frog is a setup creature: it appears in twos and threes around a swamp encounter, biting at the party's ankles while the actual threat develops behind it. Open from concealment. With Stealth plus 4 against most low-level passive Perceptions, the frog is a hummock of moss until someone steps within five feet. The real value is occupying a melee fighter in chest-deep water while the party's casters lose Concentration to the splash and the dark.

Positioning is the encounter. The frog swims 30 ft. and walks 30 ft., so it pulls a distracted PC away from the party along the bottom of a bog. Darkvision 30 ft. lets it see in murk that blinds the rest of them. Fight in the water, in the reeds, never the open clearing. Frogs flee. Once half the pack drops, the survivors croak once, dive, and don't pursue out of water.

If a frog bites and grapples a Small PC, the Swallow becomes real. The table tenses when the wizard vanishes into the frog's throat. At the end of the frog's next turn, the wizard takes 2d4 acid damage. The wizard can try to escape the grapple before that damage hits, or they can take the damage and hope it does not kill them. Either way, the frog has just turned the battle inside out.