Again, kinda based on neytirix's take on Endermen
Originally a pencil drawing. I scanned it and refined the drawing into this.

Endermen are tall, vaguely humanoid reptilians native to a dimension known as the End. They are the adult form of "Entroids" (yes, End Metroids). They protect a queen, known as an Ender Dragon, who is the sole member of their colony capable of reproduction. Despite their common name, Endermen are primarily female, with males lacking an Ender Pearl, possessing small, underdeveloped wings, and having smaller, completely white eyes. Males' sole purpose is to mate with the queen, after which they die. Males are completely docile, and only hiss when threatened. Endermen have completely lost the tail they had in previous stages, though Endermen that grow into queens will regain a tail.

Endermen owe their teleportation ability to a green organ in their hearts known as an Ender Pearl. Endermen develop Ender Pearls throughout their life cycle, kickstarted by eating chorus fruit in their pupal stage. The Ender Pearl causes Endermen and their eyes to glow purple, emitting the very energy that they use to teleport. Endermen teleport by surrounding themselves with the Pearl's energy and quickly leaping at a space, which causes them to dematerialize from their initial position and rematerialize in said space. Because of their extradimensional physiology, they are able to do this safely, unlike humans which sustain considerable injuries from teleportation.

Endermen are pack-based predators, with groups of them being called "hauntings". They hunt Endermites and Shulkers. They kill their prey using their needlelike teeth and long claws. With Shulkers, they typically wait for their shells to open so they can tear them out. If they don't, then they will forcefully open the shells to eat them. They don't usually fully consume their kills; they keep some of the consumed material in their esophagus to partially break down with Ender Acid, a fluid produced by all adult Endtroids, though only the queen has been observed using it defensively. "Ender Acid" also refers to material broken down with said fluid. The fluid is regurgitated and fed to larvae until they are able to hunt for themselves. Endermen will feed female larvae Ender Acid containing Chorus Fruit, which allows them to be able to safely eat it later in their life cycle. Endtroids are able to eat Chorus Fruit starting with their pupal stage, but stop eating fruit in their Endergator stage.

Due to the End having a highly acidic environment, strong acids do not have any effect on Endermen, and they do not drink water to survive; instead, they drink from acid ponds. The acid in these ponds has a tart, lemonlike taste, and is not recommended for human consumption due to its disastrous effects on tooth enamel and the massive indigestion it causes. The acid has also been observed to potentially cause severe heartburn. Additionally, because of their acidic nature, water is extremely hazardous to Endermen due to its high pH compared to them, and will leave them with noticeable (and potentially fatal) alkali burns. As such, water may be used as an effective deterrent to Endermen.

Endermen are largely non-confrontational, not attacking unless they themselves are threatened. They'll curiously examine other organisms while avoiding eye contact as much as possible, mimic human behaviors such as building small structures, and may even offer humans items they've found. If they believe they are about to be attacked, or if they are actually attacked, however, they will violently rake the perceived threat with their claws while hissing and screeching, only stopping when either the threat dies or they themselves are killed. They see eye contact as a threat, and breaking eye contact as seeking a weak point. Victims of an Enderman attack are typically torn apart and mutilated beyond recognition, and survivors are left permanently disfigured. Some have even compared the aftermath to a particularly violent chimpanzee attack. Because of this, it is strongly advised to avoid looking at an Enderman when encountering one, to prevent being seen as a danger, and if you must attack, to be prepared with a strong blade. Additionally, they don't appear to be provoked if one wears a mask of some sort, possibly due to their eyes being obscured. This may make eye contact difficult to discern, making Endermen remain calm even when looked at.