Froghemoth

A froghemoth is an amphibious predator as big as an elephant. It lairs in swamps and has four tentacles, a thick rubbery hide, a fang-filled maw with a prehensile tongue, and an extendable stalk sporting three bulbous eyes that face in different directions. The creature hides its enormous body in murky pools, keeping only its eyestalk above the water to watch for passing creatures. When food comes within reach, a froghemoth erupts from its pool, tentacles and tongue flailing.

Otherworldly Entities

Froghemoths are creatures not of this world. A journal purportedly written long ago by the wizard Lum the Mad describes strange, cylindrical chambers of metal buried in the ground from which froghemoths emerged, but no reliable reports of the location of such places exist. Other sages claim that froghemoths were created by the amphibious creator race called the Batrachi. It may never be known which is true, but scholars continue to debate the matter. 

Hungry from Birth

Every few years, a froghemoth can lay a fertile egg without mating. The froghemoth cares nothing for its egg, and it might eat the hatchling. A young froghemoth’s survival is most often predicated on its parent leaving it behind in indifference. A newborn froghemoth grows to full size over a period of months by indiscriminately preying on other creatures in its swampy domain. It learns to hide its enormous body in murky pools, keeping only its eyestalk above water to watch for passing creatures. When food comes within reach, the froghemoth erupts from its pool, tentacles and tongue flailing. It can grab several targets at once, keeping them at bay while it wraps its tongue around another one and pulls it in to be devoured.

Revered by Bullywugs

If a Bullywug tribe comes across a froghemoth, the Bullywug treat the froghemoth as a god and do all they can to coax the monster into their den. A froghemoth can be tamed (after a fashion) by offering it food, and bullywugs can communicate with it on a basic level, so the creature might eat only a few Bullywugs before following the rest. Bullywugs gather food as tribute for it, provide it with a comfortable lair, fanatically protect it from harm, and try to ensure that any young froghemoth reaches maturity.

Loot. 

• 1 Froghemoth Hide (Acts as a blanket. Can be carefully crafted (smith's tools) into magical Studded Leather Armor or Scale Mail that requires attunement. An attuned creature gains resistance to fire and lightning damage, but if the creature takes lightning damage, it acts as if under the effects of a Slow spell until the end of its next turn.)
• 2d2 Froghemoth Tentacles (Acts as a whip that deal 1d8 damage and has the heavy property.)
• 1 Froghemoth Tongue (Acts as a whip with a range of 30 feet. On a hit, the target is grappled and must make a DC 18 strength saving throw. On a failed save, the attacker can choose to pull the target into an unoccupied space within 5 feet of them.)
• 3 Froghemoth Eyes (No immediate use. Can be crafted (alchemist's supplies) into a Potion of Darkvision which grants 60 feet of darkvision for 1 hour.)
• 1 Froghemoth Stomach (Acts as a tent that is immune to acid damage. Can be carefully crafted (leatherworker's tools) into a cloak that grants resistance to acid damage to a creature wearing it.)
• 2d4 Vials of Froghemoth Slime (Acts as Oil of Slipperiness.)