Mindfire Tadpole.

You are infected with the Mindfire Tadpole. You gain the following features/abilities:

• Your Intelligence Ability Score becomes 19, unless it is already higher.
• Your creature type remains the same, and you are additionally considered to be an Abberation.
• You can spek, read, and write the Deep Speech language.
• You gain telepathy out to a range of 60 feet.
• Once per long rest, when you deal psychic damage to a creature, you may force it to make an Intelligence saving throw. The DC for this saving throw, is equal to 8 + your Intelligence Modifier + your proficiency bonus. On a failed save, the creature becomes stunned for 1 minute. The creature can repeat the saving throw at the end of each of its turns, ending the effect on a success.
• Once per long rest, when you use a bonus action to rage, you may choose the added Wild Magic Effect instead of determining it randomly.

An Elder Brain is connected to you via the tadpole. While you remain infected, you are subject to the effects of the Brain's Creature Sense and Psychic Link abilities. Means of destroying the tadpole remain unknown to you, and removing it will more than likely spell your doom.