Inside Team Rocket’s Castle, head for the door directly ahead, which should lead to Lusamine’s room. Unfortunately the teleporter behind the mirror is inaccessible. Follow Lillie’s advice and return to the entrance of the castle to find another way forward. You’ll bump into a pair of Rainbow Rocket Grunts all too eager to send you scurrying.
Team Rainbow Rocket Grunt x2
This time, Guzma will lend you a hand with his potent team of Bugs, starting with Golisopod. Your foes are absolute wimps, so this is mainly an opportunity to show off your prowess alongside the big bad, ex-boss of Team Skull. To make things easier, you should focus on Fearow to give Guzma breathing space.
Afterwards, the Grunts will retreat separately and, in their haste, they’ll forget to close off their escape route. Now’s your chance to give chase! Before that though, Lillie will heal your Pokémon; she’ll then retreat to the back room in case you need more healing. From here, you can venture east or west through the doors that the Grunts left open.