An oblex can live indefinitely, only being killed by an underestimated target or being destroyed as a threat to the very mind flayers that created it. In rare cases of starvation, death will also occur.

This creatures size is Medium

Having been birthed by the mind flayers you share much of their philosophy. Your alignment is Neutral Evil.

Your Dexterity score increases by 1 and your Intelligence score increases by 2.

You can speak Common, Undercommon, and one other language of your choice.

You do not need to sleep, but you still require 8 hours of rest to gain the benefits of a long rest- light action such as reading a book or keeping watch counts as rest.

Your creature type is Ooze. You are treated as Humanoid as well for spells and abilities.

Non-magical restrants do not work on you, as you can just slip right out. You can also slip through a space as small as 1 inch without squeezing. 

You gain proficiency in the Deception skill.

This creature may take the physical appearance and voice of any humanoid of medium size that it has used its Devourer of Memories trait on. It may change its form at will, but the process takes 1 minute during which the Oblex is exposed.

When you die or fall unconcious, you revert to your true gelatinous form.

As an action, the oblex can make this attack against a creature that is stunned, grappled, restrained, asleep, or incapacitated. Your true nature is also revealed during this, as colored tendrils extend from your body and face to wrap around the targets head. 

The target is forced to make a wisdom save DC 8 + Proficiency Modifier + Intelligence Modifier.

On a failure it takes 1d8 psychic damage and all attack rolls and ability checks are reduced by 1d4 for an hour. You also learn of any resistances and immunities the target may have. If performed on a humanoid you also learn of any proficiencies it may have and what languages it knows. Constructs, plants, undead, and oozes automatically succeed on this save.

On a success it takes half damage and you learn nothing.

You may only use this ability once per long rest.

After taking fire damage you gain disadvantage on attack rolls and ability checks until the end of your next turn.

Your walking speed is 20 ft.

You have a small tentacle that you can use for self defense. You are proficient in this attack, it deals 1d6 bludgeoning + your strength modifier.

Your magically created nature gives you some innate spellcasting. You gain the Friends cantrip. You may cast the Charm Person spell at 2nd level once per long rest at level 3. You may cast Hold Person once per long rest at level 5.