The only characteristic is that it has no characteristics, and the only advantage is that it has no advantages. No one will notice you if you stand in a corner, and you will be regarded as a ghost if you make a sound!
Normally, my sister would never let me step into her door. As long as I came within half a meter of her door, I would be immediately "killed without mercy": I would be hit in the back of the head with a dictionary, and hit in the back of my neck with my schoolbag... Then my "body" would be dragged away by the sister and thrown into my own room. After these bloody lessons, I would not dare to go in even if I was beaten to death.
"No, don't take it off anymore." I covered the only piece of clothing left on my body - my underwear, trying to convince my sister not to stretch out her claws on me again.