Your Intelligence score increases by 2, and your Charisma score increases by 1.

Illithids are born as larvae that infest and consume a host body. Once the host is consumed, an Illithid larva requires only days to convert their host into a new Mindflayer, and instantly reaches full maturity. Mindflayers do not age in the manner of other beings, and can survive for thousands of years.

Mindflayers live under a strict hierarchy within their hive mind. The lives of other beings are of no value to Illithids, and indeed, even the lives of their fellow Mindflayers are seen as disposable in service of the greater Hive Mind. They are almost universally Lawful Evil, and any deviation in alignment is exceedingly rare, but may be a result of whatever causes a Mindflayer to be considered rogue.

Mindflayers mutate the bodies of humanoids they possess, stretching and twisting their anatomy to the Mindflayer's preference. Your size is medium, and your height is higher than average among humans, rarely below 6 feet in height. Your internal anatomy lacks many unnecessary organs and other features, with a weight closer to 100 lbs despite your above-average height.

Your base walking speed is 30 feet. Your rogue nature prevents you from full levitation. Instead you have a fly speed of 10 feet (hover).

You can use your action to emit psychic energy to harm others in a 15 foot cone. Each creature in the area of the blast must make an Intelligence saving throw. The DC for this saving throw equals 8 + your Intelligence modifier + your proficiency bonus. A creature takes 2d6 psychic damage on a failed save, and half as much damage on a successful one. The damage increases to 3d6 at 6th level, 4d6 at 11th level, and 5d6 at 16th level. After you use your Mind Blast, you can’t use it again until you complete a short or long rest.

You have advantage on Intelligence Saving Throws against spells and other magical effects.

When Grappling an Incapacitated humanoid, you can attempt a special attack using your tentacles, which function as a natural weapon with which you are proficient. This attack deals 1d6+Intelligence Psychic damage. If this attack reduces the target to 0 hit points, you kill the target and consume its brain, gaining one of the following effects of your choice:

1. You regain one use of your Mind Blast feature.
2. You Gain a number of Temporary Hit Points equal to the psychic damage you dealt to kill the target.
3. You gain one of the target's memories. You may ask the target one question, and you gain the truthful answer within your own memories.

You may gain these benefits a number of times equal to your Proficiency Modifer, and cannot gain these benefits again until you complete a long rest.

You can speak, read, and write Deep Speech and Undercommon.