The final gym-bearing city on your Pokémon League trip, Humilau City comes quick on the heels of your seventh gym visit. You're so very close to the end - or so it seems, anyway. You're here on the heels of Team Plasma, and need to meet with Marlon, the local gym leader.
As with most leaders in Unova, however, you need to track the guy down, as he's not hanging out in his gym at the moment. Walk north through Humilau City and you'll find a criss-crossing system of boardwalks. Walk north to the first house, heading straight towards the door of the house. Marlon will jump out of the water to your left just before you enter, then head back to his gym. (It's surprisingly easy to miss this trigger spot.)
You can now follow Marlon back to the gym near the entrance of Humilau City and challenge him. First, though, we should have a look around the city.
- The house you used as a guidepost to find Marlon is the home of a Move Tutor who wants Yellow Shards. His moves skew a little more towards restoration and support, though there are a few damaging moves in his repertoire as well.
- Dip down into the shallow water and search around the middle of the houses with your Dowsing Machine. In roughly the center of Humilau City, hidden beside the edge of one of the boardwalks and in the water, is a Heart Scale.
- Behind and to the left of the gym is a Shell Bell. To reach this item you need to Surf south from the shallow water in the middle of Humilau City and look for a small beach behind the gym. Stairs will take you to the Shell Bell.
- Just south of the northeastern house and down in the water is a Heart Scale.
- Check the southwest home alone the boardwalks. Inside is a man who will trade you his Tangrowth for a Mantine. Check the trash can in this room for a Full Restore.
- Just outside the trader's home is an old fellow who will give you a Funfest Mission.
- In the northwest house is an old woman with a Mienfoo. She'll ask you to walk it around inside her home. Do this enough - it'll take a few minutes of walking back and forth - and the old woman will give you a Pearl. She won't stop you automatically, so make sure you check in with the old woman to check your progress. You can walk the Mienfoo once a day.
- Outside and to the right of the Mienfoo lady's home is a Protein.
That's all for Humilau City. You now have three options: You can take on the gym, you can head west through Humilau City to Route 22, or you can Surf south to Route 21. Neither Route is exactly teeming with Pokémon that will make your gym challenge easier, however, and since you'll need to visit them after the gym anyway we'll just plow straight ahead with taking on Marlon.