This guide explains how to detect assassins in the Expeditions: Rome game.
Guide to Reveal Assassins
Those are assassins. There’s a few ways to deal with them.
When they turn invisible, they usually move to a different spot nearby after. If you can guess where they moved to, and move one of your people directly next to them, they’ll become visible to your team. Try and box them in with your team so you can find them if you go this approach.
The other method is to use the starting sniper power ‘ranging shot’ if you target an enemy with this, it spots enemies near the one you targeted in a few hex radius. This will cancel out the Assassin’s stealth.