From the Stars Without Number Compatible – Alien Database
Bite. The bite of a heatfish inflicts 1d2 damage.
Heat Fluids. The heatfish can warm its scaly skin to reach a temperature high enough to boil water and other lighter molecular fluids. The heatfish cannot move while using this ability but can deliver its bite attack normally. A school of at least 10 heatfish is capable of boiling to death a living being, by inflicting 1d10 heat damage to the target in a single round of combat. This ability triggers only under the circumstances described in the Swarm Attack paragraph (see below).
Swarm Attack. Heatfishes attack by swarming prey and quickly biting off flesh from the victim, piece by piece. A school is composed of 2d12 heatfish, once blood sprouts from the wounds and reaches the sensory organs of the creature, the school enters a sort of blood frenzy, allowing the creatures to bite more viciously and inflict 1d2+1 damage instead of 1d2. While in a blood frenzy, if the swarm contains enough heatfish, they may trigger the Heat Fluids ability (see above).
COMBAT & TACTICS
Heatfishes move and attack as a swarm. They wait for large beasts to cross rivers or bath in waters and then they attack to bring down the prey as quickly as possible. After the first round of combat, once the first blood is spilled, they enter the blood frenzy status and their metabolism instinctively activates the ability to boil the fluids and inflict the fatal blow.
DESCRIPTION
Heatfishes have different colors to help them to blend with the fluids they dwell in. They have bulky bodies and large heads compared to the rest of the body. The mouth is filled with irregular sharp teeth and their flanks are filled with a variable number of gills (depending on the species). Their size ranges from a few centimeters for the smaller species, to one meter for those species that dwell and hunt in very large masses of fluids.
HABITAT
Heatfishes thrive in rivers, lakes, lagoons, and in some cases, they have adapted to live in coastal waters. They avoid extreme climates, preferring to live and reproduce in a temperate environment. The heatfish is an ancient and primitive form of life that emerges on planets that are undergoing the first stages of life evolution. Xenobiologists have noticed a really low degree of mutation and evolution in this species, probably due to the nature of its biological structure, which is based on sulfur.
BIOLOGY
The biology of heatfish is as ancient as it is simple, and yet it is efficient for the survival and continuity of the species. They have four main organs that support the whole metabolism, with the mouth and the equivalent of the liver being the most important. The mouth, filled with sharp irregular teeth, is capable of re-growing lost teeth within a few days, and also contains all sensory organs – the heatfish has small bulbs placed above the mouth that contains the organ of sight, smell, and hearing. The liver produces all the enzymes required to have the metabolism works, and pumps the blood as a standard heart does. The stomach is an elastic sack that can contain an amount of food equal to the weight of the heatfish. The last organ is the gland deputed to increase the temperature of the surrounding liquids in a matter of seconds, in addition, it stocks surplus food in the form of lipid molecules. The corpse of a heatfish smells of rotten eggs during the first hours of its death, however, once the smell fades away, they become edible
and are considered a delicacy.