If you knew it was bad you shouldn't have posted it

I don't know how long ago, I remember being banned from it with Choknater for spamming it for Gil back when we had an RPG, then I left, when I came back it, and MK were gone.
Riddle: We are little airy Creatures,
All of diff'rent Voice and Features,
One of us in Glass is set,
One of us you'll find in Jet,
T'other you may see in Tin,
And the fourth a Box within,
If the fifth you shou'd pursue,
It can never fly from you.
Another one:Once, I was honored as a bringer of wisdom, but am now feared as a stealer of strength.
Men shudder at my approach. Yet if they knew that they would never see me, they would cry out in anguish.
I have a foe, against whom I seek to protect mankind. But he is the stronger; I cannot protect all from him, and even those I guard will eventually fall to him.
Who is my foe?
And who am I?