Answer:
I let water fall on you while everyone else stays dry. What am I?
I don't live within a house nor do I live without. Most will use me when they come in and again when they go out.
The more you have me the less you see. Shine a light on me and I shall flee.
You do not want me when you donβt have me but when you have me you don't want to lose me.
*forward* *backwards*is what I do all day. I come in all different shapes and sizes. I can be scary and I can calm you down.
Though not a plant, has leaves. Though not a beast, has spine. Though many wouldn't need this thing, It's more valuable than wine.