Zombie Possessors also guard the tunnel between Twoson and Threed. Attempting to enter the tunnel causes the ghosts to swarm the party (and any vehicle they may be riding in), causing them to exit the same way they came in. The Runaway Five's tour bus is the lone exception, as the loud music keeps them away.
True to name, they can possess party members in a frightening manner, causing a Tiny Li'l Ghost to appear. They can also reach out with its icy hand to solidify foes.