Frogs fit ponds, bogs, rain ditches, and spring thaw. Their presence says the land is wet and alive; their silence can be ominous.
Frogs are not central in surviving Norse myth, but they are useful in folk-magic scenes, swamp hag territories, and plague imagery because players immediately understand them as wetland creatures.
Use frogs as spell components, familiar forms, warning signs around poisoned water, or a chorus that stops when something approaches.
DM-only encounter details, stat blocks, and running notes are kept at Frogs (DM).