Trojan horse

Seemingly innocuous but treacherous gift from an enemy. In Greek mythology, during the siege of Troy, an enormous wooden horse was left by the Greek army outside the gates of the city. The Greeks had sailed away as if they had retreated. The Trojans, believing the horse to be a religious offering, brought it into the city. Greek soldiers then emerged from their hiding place within the hollow horse and opened the city gates to enable the rest of the Greek army to enter and capture the city.