Marco Polo (c. 1254 – January 8, 1324) was a Venetian trader and explorer who played a small historical role in Among Thieves. He visited to the city of Shambhala, and saw the Cintamani Stone. During the events of Among Thieves, both Nate and Lazarević loosely followed his trail to gain access to Shambhala themselves.
During his travels Polo became closely acquainted with the court of Kublai Khan, the grandson of Genghis Khan. Thanks to this, Polo himself was allowed to find the city as he was granted the Phurba, about which he wrote in his journals "that the worthy seeker would be given a golden passport to conquer obstacles on the journey to Shambhala". He also included a map, to what is now known as a Nepalese city, specifying a single temple containing the secret path to Shambhala. No further trace of Polo was seen since, at neither the temple, the Himalayan monastery, nor the lost city itself. He did manage to enter Shambhala, although he did not tamper with the Stone, fearing the wrath of Kublai Khan if he would. He did however write about a gigantic sapphire in his journals, and took with him a copious amount of resin, unbeknownst to him actually the fossilized sap from the Tree of Life.
Sometime later, Polo left China with 600 passengers and fourteen ships loaded with treasure from Kublai Khan. He landed in Persia one and a half years later, with only one ship and eighteen passengers, and without the Phurba as well as most of the resin. During their journey they were hit by a tsunami, and driven deep in-land of Borneo's western coast. Although Polo's personal ship managed to survive the storm, those of the other passengers did not. They fled to higher ground, seeking refuge within an ancient temple, and ultimately all perished as they decided to consume some of the resin, going mad in the process; killing one another en masse.
I did not tell half of what I saw, for I knew I would not be believed.Marco Polo, on his deathbed in 1324
Although he recorded all of his details, he never explained what happened during the journey in his public journals. In Trebizond, Polo and his family were set upon by thieves. Although robbed of the Khan's treasure, Polo managed to hide the little resin he had left in an oil lamp, which was over time left behind and lost in a warehouse. He left a vague clue regarding the lost fleet on a note in his journals, writing that he hid his greatest sorrow in an unlikely place, and that the 'light of the Great Khan sheltered the fate of the thirteen'. This indicates that he believed it was divine retribution of a sort for taking the resin.
He also was aware of the resin's flammable, and other, properties, as within the blue flames' light the truth about the fleet's location was included, as well as the mention of a 'dreadful cargo', which he even considered cursed. Ultimately Polo managed to survive and return home, having successfully hidden his adventure to Shambhala for centuries.
Lazarević paid a lot of money to acquire Marco Polo's journals, including various other historical information relating to the Cintamani Stone. He hired Harry Flynn to acquire a Mongolian oil lamp for him, the same that Polo hid after being attacked by robbers. Flynn subsequently got Chloe Frazer and Nathan Drake on-board to perform the heist on the Istanbul Palace Museum, at the time hosting the Marco Polo Exhibit, and where the lamp was located. Nate was only convinced by Flynn's apparent willingness to double-cross his employer, and the knowledge that they would be able to find Kublai Khan's treasure and Polo's lost fleet themselves.
At the end of the heist Nate learned that Polo actually managed to find Shambhala, as well as confirming the existence of the Cintamani Stone. After the events in the museum Nate learned how much the Stone could truly be worth, and with Sully's and Chloe's help infiltrated Lazarević's camp on Borneo. There, from reading Polo's complete journals he found out that Polo never took the Stone with him. He and Sullivan also found the remains of Polo's passengers and crew, where they discovered the Phurba as well as a map with a clue to a certain temple in what is grounds for a Nepalese city. In the city Nate followed Polo's clue and uses the symbol on the ritual dagger as a guide to find the right temple.
At the end of the game Nate, Chloe, and Elena learned the truth about the Stone, and that Polo was wrong about it being a sapphire, as it was actually the fossilized zap from the Tree of Life.
In real life
Marco Polo was a Venetian merchant, explorer, and writer who traveled through Asia along the Silk Road between 1271 and 1295. His travels are recorded in The Travels of Marco Polo (also known as Book of the Marvels of the World and Il Milione, c. 1300), a book that described to Europeans the then mysterious culture and inner workings of the Eastern world, including the wealth and great size of the Mongol Empire and China in the Yuan Dynasty, giving their first comprehensive look into China, Persia, India, Japan and other Asian cities and countries.
At his return he found Venice at war with Genoa; Polo was imprisoned by the latter city-state, and dictated his stories to a cellmate. He was eventually released and became a wealthy merchant, married, and had three children. He died in 1324, and was buried in San Lorenzo.