What Am I Riddles

Question: I have all of your knowledge but could fit in your hands.

What am I?

Question: What has to be broken before you can use it?

Question: You use a knife to slice my head and weep beside me when I am dead.

What am I?

Question: Countless blades that bend with a touch,
exploited by kids who want to make a buck.

What am I?

Question: My first doth affliction denote,
which my second is destined to feel.
And my whole is the best antidote,
that affliction to soften and heal.

What am I?