Rare Monster

[ArcticVenom]

Ive been sitting in a Regular Mission and cycling through akane beach and another place to try and get the last achievement but cant get a rare monster to spawn. anybody know a faster method?

[A-tanatos-Ω]

In Epilogue, when you go to any map, some of your characters (dragons like Natsu or Wendy) can say, that they smell different monster in area. If not - try different location.

[Khelder]

You can check the chance of a Rare Event happening when you take a Regular Mission by going to Lucy's House, and checking your medals. When you start the game, it's about 20%, when you get all medals it's 50%. If you are only missing 1 medal, it should be 48%, so you should average an event every 2 or 3 Regular Requests

If an event occurs, them a character will comment when you enter the map. Sometimes the rare event will be items or a chest though, instead of a monster.

I have not yet tested whether leaving and returning resets the chance (either by removing the Rare Event if it has triggered, or allowing it to trigger again if it didn't), or whether it is set when you accept the Regular Request. However, if you have every other achievement, then taking and completing C-rank quests until it happens should be easy.

(I suggest C-rank, as I have never seen a Rare Monster in the Boundary Forest)