It is only possible to have three monsters in action at any one time but if you use ALL of the beasts in your collection at some point it ensures that they ALL gain experience.
If you have duplicated monsters, you can use one of them to create a special item to boost the rest of monsters stronger.
If you have duplicates of monsters you can always sacrifice a them to create special items that will make your remaining beasts stronger.
Always keep an eye on your monsters stamina so you can visit the nearest town whenever they are running low.
