Since their introduction to the series in the Gen 2 games, roaming Pokemon have been the source of plenty of frustration. Granted, the idea of Pokemon that move freely around the map is certainly an interesting one and helps to create an air of realism in a series that otherwise has very little. Sadly, it can often make finding and catching these elusive Legendaries incredibly difficult, and this is once again the case with Mesprit in Brilliant Diamond & Shining Pearl.
One of the three Lake Guardians, Mesprit plays a fairly important role in the games' story, and, upon its completion, players are given the chance to catch it. Unfortunately, however, it's not quite as simple as just going to a specific location and throwing a Pokeball at it, with players instead having to chase it all over the map. Thankfully though, there are a few things that Brilliant Diamond & Shining Pearl players can do to make catching Mesprit a little easier.
Where to Find Mesprit in Brilliant Diamond & Shining Pearl
Once players have completed the main story, they'll be able to find Mesprit in Verity Cavern, which is on a small island in the center of Lake Verity. To get there, players should head over to Twinleaf Town and then leave via the northern exit. Heading west here will lead to the lake, and then it's just a simple matter of using surf to reach the island in the middle and walking through the archway to get inside the cavern.
Upon entering, players will find Mesprit hovering in the center of the cavern. Unlike other legendaries, there's no need to save before interacting with it, as the second that players do, it will disappear and fly away. Professor Rowan will then show up and suggest that the player follows the cute little Legendary, revealing that they'll be able to track its movements by using the Marking Map app on the Poketch. Unfortunately, it's not quite as easy as it sounds.
How to Find Roaming Pokemon in Brilliant Diamond & Shining Pearl
Granted, players can get an idea of where a roaming Pokemon is at any given time by bringing up the Marking Map screen on their Poketch. They won't just be able to fly to the marked location, however, as using Fly typically causes roaming Pokemon to move to a completely different part of the map. In fact, even traveling on foot from one screen to another usually leads to them moving to a new area, though they'll typically only move by one or two routes at a time while the player is walking.
Rather than trying to chase a roaming Pokemon, it's actually far easier to manipulate its movement to force it to a specific location. A great way to do this is by traveling to a city with multiple exits (preferably not ones that involve passing through caves or buildings) and positioning the playable character near one of the invisible borders that connect the city to one of its neighboring routes. It's then simply a case of repeatedly crossing over the invisible border to force the Pokemon to move and waiting until it appears on one of the routes that are connected to the city.
Jubilife City is probably the best place to do this in Brilliant Diamond & Shining Pearl, as it has multiple exits and each one has patches of long grass in which the roaming Pokemon can spawn. Once players find themselves on the same Route as the roaming pokemon, they should save their game and then wade into a patch of long grass in the hopes of encountering it. The chances of this happening are actually quite high, but, if a different Pokemon shows up and the roaming Pokemon has moved on after the resulting battle ends, players can simply reload their save file and try again.
How to Catch Mesprit in Brilliant Diamond & Shining Pearl
Catching Mesprit is very similar to catching other Legendaries, only with one major difference: the first chance that it gets, Mesprit will run away, forcing players to start the process all over again. To prevent this from happening, players can use a few different strategies, the most effective of which is to use a Master Ball. Alternatively, players can use Hypnosis (learned by Pokemon like Gengar, Hypno, and Gallade) to put it to sleep or Mean Look (learned by Pokemon like Gengar, Golbat, and Dusknoir) to prevent it from escaping.
Those who don't have access to either of these moves and don't feel like tracking down a Pokemon that does can take a slightly different approach. It's actually a faster method too, though involves repeatedly reloading and so can be a little monotonous to carry out. All the same though, by throwing a Quick Ball at Mesprit straight away and then reloading their save file in the event that it breaks free, players should be able to catch Mesprit in a matter of minutes. They can increase their chances even more by lowering Mesprit's HP with a move like False Swipe (purchasable as TM 54 from the Veilstone City Department Store) first, though this will mean finding Mesprit again after it flees.
In the event that Mesprit flees, any damage that the player inflicts will carry over to their next encounter with it, allowing players to gradually chip away at its health if they'd prefer. Should they go too far and knock the Pokemon out though, it will disappear from the map entirely and will only reappear if players defeat the Elite Four again. This only works for Legendaries that have been knocked out though, so those hoping to farm Legendaries using this method are out of luck.