I start with an E and end with an E, and we can contain thousands of letters.

Man and Lion alike are oppressed by me When you are not my target, I'm less threatening than a box The key to escape my grasp is unnattainable for those oppressed by me

I can be hard, I can be soft, Made from wood, with age I rot. But crack me open, take a peek, Inside, stories I shall keep.

I cuff the creative and puzzle the physicist. I tempt the cat. How can you be certain of my contents until they're free of me?

In forests of dreams, I reside, With button eyes, arms open wide. My hug's a warm affair, No growl, just tender care, A childhood friend in whom you confide.