Mind Flares Finish "ceremorphosis" by the age of 9. They tend to live linger than humans but they do live to be around 120-130. Assuming the mind flare is in a optimal living scenario they can live to 135 years of age

With the new body of an Mind Flare your eyes are stronger, you have superior vision in dark and dim conditions. You can see in dim light within 80 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 flares are usually around 6 foot maybe a bit taller but around the size of a human. Your size is medium

Your base walking speed is 30 ft

Your Wisdom score increases by 1, and your Intelligence score increases by 2. but your charisma score decreases by 1

Sadly the only way one can fill there need for food is to devour someone's brain. The best source of food is humanoid brains. 

The rate of which one eats brains would normally be once per month in a thriving hive, but for a rogue Mind flare once every two days a humanoid brain Is needed to fend off hunger.

You can use this action twice per day (once per short rest) 

Due to the transformation of your body your mind and brain has expanded a large amount giving you a 'resistance to Psychic damage from Magical and Non Magical attacks

You know the Mind Sliver cantrip. When you reach 3rd level, you can cast the Mind Spike 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 Phantasmal Force 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 speak, read, and write Common, Deep Speech, and have one way telepathy 50 ft