As of the 1.16 update in Minecraft, there are 31 unique mobs within the game. Some of these mobs have much higher spawn rates than others, and some mobs also are known to only spawn in particular places.
In combination, these factors make for some particular mobs that are far less known within the game, even seasoned Minecraft players may not have heard of some of these mobs. This is primarily due to never having come across them during their adventures within the game.
Note: There are no objective, most unknown mobs in the game; however, some have been picked out based on the writer's sole opinion.
The rarest and most unheard-of Minecraft mobs
#5 Brown Mooshroom
While regular Mooshroom is somewhat rare, they are still a fairly well-known Minecraft mob among players. Mooshroom feature a striking resemblance to a cow. But instead have a red and white complexion.
On the other hand, Brown Mooshroom are rarer and much less known by even veteran Minecrafters. A brown Mooshroom will only spawn if a regular mushroom is similarly struck by lightning to a charged creeper. Unless done on purpose by players in creative mode, this set of circumstances has an almost negligible chance of occurrence.
Giants resemble zombies esthetically, with the only difference between them being the clear massive size difference. Giants are not normally seen in the game, making their existence relatively unheard of between Minecrafters.
However, giants use it to spawn naturally and quite commonly in experimental development builds of the game, hence why their data model still exists within the Minecraft code; however, it is currently completely unused within the vanilla game. Giants are about 12 blocks tall and are a factor of 6 times bigger zombie model.
#3 Skeleton Horse
Skeleton Horses are bought into a Minecraft world in the same way as charged creepers by getting lightning struck. When the rare event of a horse getting struck by lightning occurs, multiple Skeleton Horses will spawn with Skeletons riding on top of them.
After being spawned, this group of skeleton horses will go onto roam around together in the wild. Skeleton Horses will naturally be automatically despawned after 15 minutes, making them an even more rare find.
An Endermite is a mob that has a 5% chance to spawn upon throwing an ender pearl. They don’t really have any real practical use within the game, the only thing they tend to do is annoy players through their feeble attacks.
Endermites are very similar looking to silver fish except they’re purple and are a little bit smaller. Endermites will also naturally despawn after 2 minutes, no matter the circumstances, making them a vastly more unknown and rare Minecraft mob.
Vexes are flying hostile mobs that can sometimes be found in rare, naturally spawning woodland mansions. They are summoned only in small groups by spell-casting evokers.
Vexes spawn during the summoning attack phase of an evoker, the evoker starts this attack by summoning white smoke along with a horn sound. When summoned, three vexes appear.
Many long-term Minecraft players will likely have never come across a vex before while playing. This is primarily because vexes can only be spawned by an evoker, which in themselves is a rarity.
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