Synchro Machine

The Synchro Machine is a feature in The Terarium in the Indigo Disk DLC that allows for you to sync up with your Pokémon. To use it, you need to complete a task for Synclaire and complete her research.

Once you have obtained the Synchro Machine, you can activate it by sending your Pokémon out of their Pokéball, holding the L button down and then pressing the R Button. This will allow for you to fully take control of your Pokémon in the overworld and can be done only in the Terarium.

When you have synced with a Pokémon, it basically controls much like you would as normal, being able to move around at the speed of the Pokémon so a Pokémon that moves fast like Varoom will move fast while a Pokémon that moves slowly like Alcremie will also move slowly. You can pick up items in this mode as well

A Pokémon is also restricted to how they would be in Auto Battle so a Pokémon that is unable to fly or swim will be unable to go on water.

When playing, you can attack wild Pokémon and get experience for doing so. However, unlike Auto Battle, you can attack and knock out Shiny Pokémon and, if a Shiny Pokémon spawns by the Pokémon and you're far away from the player, that Shiny Pokémon will despawn by the time the player reaches it.

You can also play with a ball by pressing the ZR button. This sends out a large Marill Ball that you can knock around. If you have friends playing, then they too can interact with it.

Some Pokémon are ones that can fly and with this, when they move off an edge such as a cliff or the top of a mountain, they won't immediately fall down but will have a gradual drop which allows for you to basically fly without gaining any further altitude

If the Pokémon can both fly and walk, you can toggle tis with the B button while standing still.