play the devil with

child's play

Something particularly easy or simple.

dance with the devil

To engage in risky and immoral behavior.

devil dancing

Risky, reckless or potentially immoral behavior.

devil in disguise

A person or thing that appears to be good, honest, or upstanding, but is inherently nasty, evil, or damaging.

devil lies in the details

Synonym of devil is in the details.

folk devil

A person or type of person blamed by the public for various ills, as during a moral panic.

give the devil his due

To acknowledge the positive qualities of a person who is unpleasant or disliked.

go play in the traffic

To go elsewhere and feel free to engage in risky behavior; to get lost.