Wilderness Units in the wilderness run the risk of attack by bandits, fiends, or monsters. A stack with 25 soldiers will be safe from most wilderness attacks, but very dangerous monsters exist that can challenge even a very powerful stack. Some monsters are dumb, and launch unthinking attacks against anyone who comes near, even if the attack is suicidal. Other monsters are smarter, and avoid attacking stacks they think are stronger than they are.
All monsters fight to the death once they attack.
Most monsters will kill and eat any prisoners they take. A few, like bandits, will merely strip prisoners of all their valuables and turn them loose again. Some monsters will rush to join in when they see other monsters attack. For instance, wolves run in packs and will usually aid other wolves. Bandits are quick to take advantage of any combat, and may join in a battle if they see an opportunity.