Return to the main desert and head about a screen North, then turn to the East.  You’ll pass a backpacker to the South who rattles about the Mirage Desert and Go-Goggles (a nice little reference to the third generation games) before you spot another one looking for a battle on a hill just North of you.

Battle: Backpacker Walt (528 Poke)
Opponent: Sandile Lv 22

Walt’s Intimidate Sandile isn’t too threatening, so flatten him out and move on.  When you reach the East edge of the desert, head North a bit and go West again- you’ll climb a hill that has a ruin entrance on it- and a creepy guy.

Battle: Psychic Tommy (854 Poke)
Opponent: Woobat Lv 22, Yamask Lv 22

Beware of his Yamask- Mummy can be a horrible affliction on the wrong pokemon (though a hilarious boon to a few), and it uses Will-O-Wisp to virtually ensure a burn if it can.

Make note of the ruin entrance here, then continue to the West.  On the North side of you will appear a Ranger who babbles about buried treasure and lingering around for a year to find it, and then gives you a Funfest Mission for your Entralink.  Keep going and you’ll find a buried castle turret, and another Psychic looking for a fight.

Battle: Psychic Future (Female) (736 Poke)
Opponent: Munna Lv 23

Munna isn’t much if you use physical attacks to clobber it- particularly as this trainer likes to hit Imprison on anything even capable of using Psychic moves.