What am I?

I start with M and end with X. I have a never ending amount of letters. What am I?

I am in heaven but not in hell. I’m in the devil but not in god. I’m in the river but not in the sea. What am I?

In prison I will be found, But I’ll never be in court, Unless there’s more than one. What am I?

If I eat I'm fine but if I drink I die. What am I?

Riddles and Answers