Hetfish

Hetfish, sometimes called hotfish by sailors, were a species of rarely encountered somewhat intelligent fish, "wonders of the undersea".

Description
Hetfish were small aquatic creatures between and  in length. They had a very prominent scale coloration of silver and orange as well as distinct unappealing bumps and boils that covered their entire bodies. Overall, they had a similar body shape to piranhas but lacked their razor-sharp teeth and underbite.

Abilities
The main abilities of note were hetfishes' super-heated bodies. The temperature rose beyond, turning the waters around them into steam. Some hetfish were able to not just boil their opponents via heating the waters but also could set their targets on fire with magical flames. These flames could not be extinguished by any mundane means as long as the target remained surrounded by the swarm. It only could be done via spells such as quench, or by moving away from the heated beasts.

Behavior
Hetfish possessed humble intelligence, on par with smartest dogs or dullest gnolls and were attracted to shiny and glittery things, such as gems, as well as movement. Their dens could often contain such valuable items as each individual fish at one point or the other, brought a precious stone back into the lair. The fish were intelligent enough to learn that these pretty baubles could often be carried on board ships that sailed through their territories. This often led to hetfish dens attacking and rams mine vessels to get their fins on gems and other shiny items.

Hetfish did not have a language or similar ways of communication.

Combat
Hetfish turned aggressive the moment their den was disturbed, swarming the trespassers. When defending their homes, the entirety of the den entered the conflict. They swarmed around their targets, biting and boiling them alive, and continued to attacks long after the intruder was dead and cooked. These creatures were deadly as their mere presence in the water around the opponents was deadly. The boiling steaming heat could leave blisters when the fish's opponents were as far as away from the den.

Ecology
Hotfish were extremely adaptable and could inhabit both fresh and saltwater water reservoirs; furthermore, they could survive and even thrive in any climate, be it frigid arctic or boiling sulfurous hot springs.

It was believed that the steam created by hetfishes' bodies was required for them to be able to breathe, and they were unable to survive underwater otherwise. Sages did not know how these beings could buoy themselves in the water nor how they produced such deadly heat within their small bodies. Sages believed that their biology was similar to that of a remorhaz and many sages and alchemists were willing to offer from 10 to 100 gold pieces for living specimens to study.

This mysterious heat-generating ability also left hotfish with civilized races as their main threat. Races that dwelt underwater, such as tritons, hunted hetfish unrelentingly, considered them a major environmental threat. Inhabitants of the surface world hunted hotfish primarily for the precious gems they accumulated and protected their naval vessels from being sunk.

These fish could be found dwelling in solitude or gathering in communal dens numbered between two and seventy individual creatures. They tended to live in coral dens. Each den's territory depended on the size of the community, on average being in radius per fish. Creatures of any size or aggression levels were considered prey by hetfish, with very few creatures that lived within their territories.

When encountered in subterranean locations and smaller pools of water, hotfishes' presence could be deducted by the state of constantly boiling water and the copious amount of steam produced. Such caves were filled with condensation that accumulated on the walls and ceilings and trickled back into the pools. Some derros found a way to harness that heat to warm their homes during colder months. However, they had to head with constant humidity such heating brought.

Relationships
Hetfish were known to serve a dwarvish deity Abbathor, the Great Master of Greed.