Reprobate

The Reprobate is a species of amorphous sporovid that can absorb the mass of other beings into its own.

=In fanon games=

In Pikmin: Dual Worlds
The Reprobate is a rather elusive sporovid in Pikmin: Dual Worlds that can take on many forms beyond its basic one. It is a somewhat amorphous sporovid best described as a tough, spongy mass of tannish-purple flesh coated in small barbs and tendrils. It takes wildlife, such as creatures, Pikmin, assorted flora, and even other sporovids, and physically attaches them to its body or within it. Targets can fight back against the Reprobate, dealing damage to it, although the creature dying from them is unlikely. Reprobates may be found walking about, scaling walls, attached to virtually any surface, or even floating on or in water. It tends to attempt to assimilate creatures with long-ranged or projectile attacks, although it will also do so to short-ranged or docile creatures as well. The forms of beings a Reprobate has assimilated into its mass are displayed on its body. The sporovid is only as strong as the creatures it absorbed, however, and killing enough of them makes it possible for the remaining creatures to damage the Reprobate itself. Fire, electricity, acid, jets of water, and offensive fauna are all effective ways to dispose of a Reprobate. Pikmin are most effective against the Reprobate itself as they deal the most damage to it, although they are still subject to attack. Some assimilated creatures are passive, however, and pose no threat whatsoever; the several Puffmin often trapped within a Reprobate are one such example. A Reprobate itself may also be docile, and if this is the case all entities composing it will also be passive. In such a state it instead tends to act as a physical barrier. When outside of the range of its other attacks, a Reprobate will launch spore-filled projectiles at its targets. Defeating them is rather difficult, especially without casualties, and as such, there is an achievement attached to doing so. There is also a small subspecies called the Affliction that tends to latch on to a singular creature and act more in a symbiotic way, in that it gets nutrients from its host and is better protected but in exchange doesn't take it over and covers some of the host's weaknesses.

Olimar's notes
This terrifying creature absorbs other still living creatures into its own body. I notice that nearly all of them contain the remnants of Pikmin corrupted by spores. Despite that, I don't see any Pikmin, living or possessed, roaming around. It would be nearly impossible for any Pikmin to make it here on their own, and if any attempted to do so I would have found their bodies walking around outside. However, this cavern seems to be mostly impossible to escape from without outside help. If there are Pikmin here.. then where's..?

Louie's notes
If you're brave enough then go ahead, but even I wouldn't try any of these. That's just a surefire way to end up a walking husk, just like any Pikmin you happen to lose to the spores.

Alph's notes
Structural flaw: varies on instance, always is weak to fire, water, electricity, acid, and explosions Weight: unknown

This thing reminds me of that "gray goo" theory. It seems to eat just about anything. If you presented it with a rock it would probably end up assimilating it into its own body and using it to crush others. I don't enjoy being near their bodies, for all I know if you don't completely destroy them they might just get back up.

Brittany's notes
Nope, no thanks. I don't want anything to do with this.. thing. I don't like how it just wriggles around like that, and I don't personally want to become a pile of flesh and mold.

Charlie's notes
These things absorb the bodies of other creatures, meaning that they tend to have a wide variety of attacks. Your best bet is to stay away from them entirely. If you do find yourself in a situation in which you need to kill one, your best hope is to find some sort of environmental hazard to take advantage of, like fire geysers, pools of water, or some other creature. Explosions are also a good way to deal with them, but that goes for just about anything. The Pikmin don't seem to want to go near it. I could say the same.