Currently I'm only fiddling with ideas on how I should actually accomplish this.
I have random encounters on the world map and visible monsters everywhere else. Some of the monsters are underground creatures and it wouldn't fit in the game if those monsters would be encountered in the world map so thats why you'd need to be inside a dungeon to find those. I also don't like the fact that when player clears a dungeon and comes back the monsters have spawned again. Running back and forth between the same map just to get the visible monsters spawn kinda ruins the immersion imho. When visible monster is dead, it stays dead (with some exceptions of course, like an area with some sort of infestation that spawns those monsters if the areas quest is not completed).
This is where the item would come in to play. Monster Attractomator-3000™. With that item you could attract the attention of monsters by allowing random encounters to occur. Or perhaps an easier way (and more convenient) of doing this is to make the item call common event with a timer (or no timer) and have it call battle process "same as random encounters"?
But if there'd be more powerful version of that item, like Monster Attractomator-4000™ to attract more powerful monsters, how'd you make that since the other item already uses the random encounters pool? And what if you'd tried to use it on a location that has no enemies like in a town?
Why all this? Because the player might have missed some skill for his blue mage, some stealable skill, item, ingredient, material etc, or just want to level up his characters.