Quos ego is a Latin phrase that means "whom do I threaten". It comes from a famous quote by the ancient Roman poet, Virgil. In the context of the poem, the character saying this phrase is a powerful and intimidating person who is warning others not to mess with him, or else they will face the consequences. It's like saying "don't mess with me, or else you'll be sorry". So basically, it's like a warning to people that if they don't behave or do what someone wants them to, they might suffer the consequences.