EastScape Wikibuilt from the game itself

Marked Cards

Pete thinks the Counters in the Mire are marking the house's cards. Eight of them, and bring him three marked cards.

“Eight of them, and bring me three of the marked cards so I can show Dex.”

They're in the Mire's east, counting. They count you too.

Steps
  1. Defeat 8 card counters
  2. Bring 3 marked card to Parlay Pete
Reward2,000 tickets, 1,500 Thieving xp, 800 Melee xp