Pink slime
From D&D Wiki
Ability Score Increase Choose an ability score to increases by 2 or two ability scores to increases by 1
Age They are immortal.
Alignment Slimes tend toward chaos due to their fluid nature, but may be anywhere on the spectrum of good and evil, depending on how they control their instinct to devour everything.
Size When they are in their base form, they are considered small, when in a shape they shift into, they take on the size of the form. I.E. - Humanoids are medium size.
Speed Your base walking speed is 10 feet. Unless in another form.
Languages You can speak, read and write Common, as well as the language of your choice.
Slime form abilities:
Amorphous Your fluid body allows you to move through spaces as narrow as 1 inch without squeezing. Non-magical restraints do not work on you, as you can just slip right out. Your racial type is Ooze.
False Appearance As an action, you may drop yourself into a puddle, while you remain motionless, it is indistinguishable from an oily pool or wet rock. In this state, you are prone and your speed is 0.
Fluid Body Do to the fluid nature of your body, you cannot wear conventional armor or jewelry in your true form. Instead, you have a base AC of 10 + your Constitution modifier.
Internal Storage Slimes can form pockets within their gelatinous body to carry objects. While you can have several pockets within your body, they collectively have up to a volume of 1 cubic foot. For example, you can hold a single short sword or several small pouches or a handful of arrows or a pair of daggers. Another creature can attempt to wrestle an object from inside your body through an Athletics check contested by your Acrobatics or Athletics check. You may use this trait even as a humanoid though the objects must fit within your body.
Blindsense You have a blindsight range of 30 feet but are blind beyond this radius.
OTHER TRAITS:
Devouring Mass You may also choose to devour a creature that died no more than 1d4 hours ago or enough of their blood to gain its form for your Shifting form trait.
Shifting Form As an action, you may change your appearance to that of a medium-sized humanoid that you have consumed the body or enough of the blood of.
Lasting Absorption When you devour a creature with Devouring Mass, you gain one class feature and racial feature they had permanently. You may only gain features that are equal to or less than your current level.
Slime Nature
You are immune to disease, being poisoned, and poison damage. You do not need to breathe. Instead of sleeping, you enter an inactive state for 4 hours each day. You do not dream in this state; you are fully aware of your surrounding.