Monsters Olympia is roamed by many sorts of monsters.
Monsters often attack player stacks.
Garrisoned provinces are even safer, as the mere presence of an active garrison keeps some monsters away. Very few monsters will enter a city, making cities the safest places of all. A stack with 25 soldiers will be safe from most attacks, but very dangerous monsters exist that can challenge even a very powerful stack. Missile weapons are also valuable against monsters, as few monsters have the intelligence to take advantage of missile combat. Dumb monsters will attack any stack they outnumber.