>>48787743>You use Defog and then they start to spawn in areas of the underground just like that?No. Once you reach certain points in the game more Pokemon become available in the Underground
>Start>Get Strength>Get Defog>Get 7 Badges>Get Waterfall>Get National DexMunchlax can then spawn Underground but is rare. If you use statues to your advantage he'll be more common but I've gotten a few just by going in and out until it spawned. Took me less than 3 minutes without statues
