Unnamed is around 6'6", not that anyone has been able to measure their height anyway. they have bright blue pulsing skin (sort of like the disco sack skin from lbp2, but always blue. Yes that's the equivalent I'm going for and yes I'm sticking with it); their eyes are also large white orbs which glow as bright as a flashlight (but do not let out a beam of light).
Unnamed hasn't spoken to anyone yet, so it's not known how they act in social situations. How they are able to speak English, we may never know.
Unnamed has many theories written about them in official documents regarding their existence. They are widely studied anonymously as nobody seems to remember seeing them after they notice them and all footage contains mysterious blurs where Unnamed should have been.
Ability - Definition