Herein are presented three variant froghemoths. Now, you may find the original Pathfinder Bestiary froghemoth a bit bizarre, both in appearance and behaviour, but if you find them of interest these variations fit in rather nicely, being just as weird in their own ways.
First up is the arctic froghemoth, with chilly breath and barbed harpoons on the end of its tentacles. They are ambush predators and although they seem well-adapted to their frozen environment still never seem completely at ease there.
Then we have the volcanic froghemoth, which makes its home anyplace warm: its name stems from its high body heat and ability to spit flame - although from the sound of it they would probably enjoy an active volcano. As most adventurers steer clear of such places, you may choose to put them elsewhere. This is facilitated by the fact that they are not ambush predators but much more active in search of their prey.
Finally comes the deep froghemoth. This gargantuan creature dwells underground and is covered in a thick acidic slime. It also has a symbiotic relationship with a rather nasty fungus (which apparently does not mind acidic slime!), and spreads its unpleasant spores around with gay abandon.
Ever since froghemoths were first recorded, there has been speculation about their origins. These variations suggest that an extra-planetary or extra-planar origin may indeed be likely, and that their grumpy nature stems from being trapped somewhere, to them, unpleasantly alien! Whether they have descended and diversified from a single group transported to your campaign world, or are unlucky enough to pop through from someplace else on a regular basis is up to you, as is their point of origin and any possibility for adventurers to make the reverse trip!