Your Intelligence score increases by 2. In addition, one ability score of your choice increases by 1.

Think of what race of humanoid you took over as a tadpole. A Half-orc may give you a +1 in Constitution or Strength, while a High Elf would give you a +1 Intelligence or Dexterity.

Mind Flayers can live to be around 125 years old. The first 10 of which they spend as a tadpole in a brine pool.

Mind Flayers have one goal in mind, to rebuild their lost empire. They will do anything it takes to achieve this goal. As such you tend towards evil. Their society functions as a hive mind, leading you towards being lawful.

Mind Flayers born by overtaking the body of a humanoid in a process called ceremorphosis. Your size is Medium.

Think about what type of humanoid you took control of as a tadpole. If it was a large humanoid you may be closer to 8 feet tall and weigh around 250 pounds. If it was a small humanoid you may be closer to 4 feet tall and weigh around 125 pounds.

Your base walking speed is 30 feet.

Your creature type is aberration, rather than humanoid.

Accustomed to life underground, you have superior vision in dark and dim conditions. You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can’t discern color in darkness, only shades of gray.

Mind Flayers prefer to use telepathy to speak, however, being away from the colony has reduced your ability to speak in this way. You can speak telepathically to any one creature at a time within 60ft. You do not need to share a language with the creature, but the creature must be able to understand at least one language.

For more detail on how your telepathy works, read the Telepathy section in the introduction of the Monster Manual.

Your Tentalces are natural weapons, which you can use to make unarmed strikes. If you hit with it, you deal psychic damage equal to 1d4 + your Intelligence modifier, instead of the bludgeoning damage normal for an unarmed strike. You may also use your tentacles to grapple one creature at a time. Doing so does not limit your ability to use your tentalces for unarmed attacks.

When you attempt to grapple a target with your tentacles you follow normal rules for grappling, except that you make an Intelligence (Athletics) check contested by the target’s Strength (Athletics) or Dexterity (Acrobatics) check.

Due to leaving the Mind Flayer colony your Psionic powers have be heavily weakened. You are no longer able to use your Mind Blast ability and instead can only do small amounts of physic damage to an opponent at a time.

You know the vicious mockery cantrip. When you reach 3rd level, you know the [Tooltip Not Found] cantrip and can cast the detect thoughts spell once with this trait and regain the ability to do so when you finish a long rest. When you reach 5th level, you can cast the levitate spell once with this trait and regain the ability to do so when you finish a long rest. Intelligence is your spellcasting ability for these spells. You can cast these spells psionically. If you do so, the spells don’t require verbal, somatic, or material components.

You can speak, read, and write Deep Speech and Undercommon. You also know how to read and write Qualith. For more information on Qualith read the Qualith section in Volo's Guide to Monsters.

You have memories of the race your body once was. You learn one language of the race you took over as a tadpole. For example if your body was once an Elf you would know either Elvish or Common.

Mind Flayers lack the biology to speak through conventional means. To provide the verbal components for spells or to speak to groups of people without your telepathy you have to shove one of your tentacles into your throat to simulate a tongue. For more details see the Speech section on Mind Flayers in Volo's Guide to Monsters.

Most creatures you interact with will find the sound of your voice disturbing. When speaking to others you make all Charisma Ability Checks with Disadvatage.

A Mind Flayer's diet consist only of brains of intelligent humanoids. As such you do not need require food. However, if you go any longer than one month without consuming the brain of a humanoid with an intelligence of 4 or higher you will starve to death.

Although you can settle for the brains of dead intelligent humanoids, doing so doesn't provide the same sustenance as that of living creatures. Consider the brain of a dead humanoid to have a -5 to its Intelligence score.

To consume the brains of a living humanoid you must kill it with your Tentacles attack or use your Tentacles attack on a humanoid that has been dead for no longer than 1 round. Doing so allows you to fully consume the psionic energies within an active brain.

To see how long you must go before your next meal, consult the table below.