Stronghold 5-5, a Prometheus has been confirmed to be deployed. Those fuel tanks are your best shot at knocking it out.

Prometheus spawned in and approached your teammates, And then started to use his flamethrower and burn them.

He also used his jetpack and launched himself into your other teammates.

He noticed you and then launched himself towards you and turned on his flamethrower.

You eventually noticed his weak spot is his gas tanks, If they explode you'll surely defeat him.