You enter a region, then you will randomly enter fights.
But the fights will take place in a arena. All your units will be teleported to the arena to fight. And when all enemies are dead. You will be teleported BACK to the place you were. And if you summon a elemt or other things inside the arena. They too will be teleported to the place you were befor the fight
I am currently doing that chrono trigger type thing in an rpg i am making. when you approach the monsters, the camera bounds change but you are still in the same area. That way you can use the terrain to your advantage in different strategic ways.