We decided to try the quest again and managed to finish in about 24 minutes. However, we waited till 28.8 minutes before submitting the quest for completion. We received the standard reward package as listed earlier and because we finished within 30 minutes, we received 3 Halloween Pumpkins Hats and also had the option to choose between 3 permanent costumes or a set of experience cards. We chose a Deadly Cross for our Captain Adelina as their colors matched quite well.
For the third try, we had to defeat 75 Villains and 110 Swamp Spider Crabs. We were initially confused by where the Villains were so it took quite a few minutes to remember that they were found in Topolo Durga. Defeating the Swamp Spider Crabs weren't easy so we were unable to finish within the 30 minutes. The reward was the standard reward as given in the previous entry.
Upon closer inspection of the Level 90 Experience Cards, we discovered that they gave 560,000 experience each. That's far above even level 100 experience cards.