What Am I Riddles

Question: What can you serve but never eat?

Question: Lose me once, and i’ll come back stronger Lose me twice, and i’m gone forever What am I?

Question: When I come in, someone else leaves, I know everyone, yet no one knows me. I'll meet you all only once in your life, Causing mayhem and mischief and sorrowful strife. What am I?

Question: What is square and green?

Question: I am god to many people despite not being a spirit. I am what people kill over, lust over, and fight over. I am not God or the Devil, but a mere material that people need endlessly. What am I?