Here is a more detailed version of the treasure hunt quest. Rill suggested to use the existing TMW lore by including Cerise and Blanc. Please share your thoughts. Next I'll write the full NPC dialogues.
Back story:
Captain Cerise acquired a treasure map. She and her crew went on an expedition to find the treasure but encounter a violent storm that broke her ship's main mast. She head to Tulimshar for repairs. With no treasure aboard the ship, Cerise and her crew lacked the funds and materials for the repair. Karnor, second in command, suggested shady ways to obtain the funds and materials. This led to tensions between Cerise and Karnor. He started to talk behind Cerise's back to other crew members. His plan crystallized when he poisoned Cerise's meal, stole her treasure map and fled with the crew members he influenced : a mutiny !
Karnor then stole a merchant ship, repurposed it as pirate ship and sailed to the treasure location. He also incorporated Reyma to his plan. Reyma had joined Cerise so she could receive her share of the treasure and pay for her tuition at MIT and accommodations frees. Karnor gave her money to make her his land spy. She must regularly send light signals from MIT tower at night to inform him of merchant ship movements and Cerise's activities.
Unfortunately for Karnor, the map he stole from Cerise was a fake one she drew just in case. After his vain search for the treasure, he met Blanc. Both pirates decided to team up to take Cerise's map, sink her ship and share the treasure. Blanc was happy to take his revenge on Cerise while making money. Karnor needed the help of Blanc to ensure victory against Cerise.
In game:
The player see a ship with a broken mast docked at Tulimshar port (map1). He/She can climb aboard the ship (map2). Cerise is unconscious in the captain's room, poison particle effect shows up near her head. NPC crew members worry about her and tell some part of the back story to the player. (We need names for the crew loyal to Cerise. If you know some, please share.)
When the player bring a [Slow Poison Potion] to Cerise, she wakes up and tell the full story. She explains that Karnor stole a fake map. She ask the player to bring the following materials to repair her ship: 250 [Raw Log], 150 [Cotton Cloth] and 10 [Iron Ingot]. In exchange for the repair, she'll share the treasure with the players and ask that at least 5 braves players joins. Any player in Cerise's ship inside room will be included in the crew if he/she wears one of the following hat: [Bandanna], [Pirate Hat], [Sailor Hat], [Captain's Hat], [Corsair Hat], [Eyepatch]. Once the quest starts, the players can wear any hat they want. The idea here is to create a visual effect where the player crew look like an actual group of pirates 
Cerise ask all the crew (NPCs and players) to go on the upper deck to maneuver the ship (map3). She then retrieves the true map from inside the ship and join them on the upper deck. After a short time at sea, 2 ships approach hers from the West: Karnor attacks her rear and Blanc attacks her North side.
Karnor: It was a real pleasure to steal the map from you.
Cerise: You'll rot in prison for that ! And for your mutiny !
Karnor: Your fake map mad me lose a lot of time at sea but I met a good acquaintance of yours.
Blanc: Ah poor Cerise. Most of your crew left you. How unfortunate.
Cerise: Blanc, you're were behind this mutiny from the start.
Blanc: Humm... I wish.
Karnor: It's now time to handover the real map. I'll enjoy searching you again if you resit.
Once the attacking ships are in place (map4), the players fight the troupes coming from both ships.
After the players won the fight, Blanc sails away but Karnor can't move from his attacking position.
Karnor: Blanc ! We had a deal !
Blanc: You're not fit for piracy.
Cerise captures Karnor and his crew. She attaches Karnor's stolen ship to hers and reaches the treasure island. They can be some weak monsters on the island. The players then open the treasure and each player receives 200 [Coin Bag]s, 30 boss points and 33% daily points. Giving players coin bags aims to create a more tangible reward that getting gp directly.
Back at Tulimshar, Karnor and his crew are sent to prison. (We probably need a prison map).
Reyma hears about her patron beings in prison. As she'll need money, she tries to fund her studies herself. She ask the player to bring her 250 [Shadow Herb]s for her research. One week later (real server time), she finds a way to alter the concentration potion. She then sells [Dark concentration potion] for 100gp + 1 [Concentration potion] + 1 [Shadow Herb] + one of the following [Candy Cane], [Candy], [Xmas Candy Cane] or [Decor Candy] (the burned sugar smell has to come from something).
Reyma's quest can be postponed to when the developers feel comfortable introducing the dark concentration potion.