Tulum was a former Mayan city on the coast of Mexico, later used as the headquarters for the Caribbean Assassins up until 1722, at the conclusion of the Golden Age of Piracy. It was the location of an armor made of First Civilization metals, locked behind a door that required gathering the Mayan stelae scattered across the Caribbean to open it.
Becoming an Assassin stronghold
Tulum was founded by the Mayans thousands of years ago, on the coast of the Yucatán Peninsula. It consisted of a handful of temples and several smaller stone buildings. The largest temple, nestled at the heart of the city, housed an ancient underground cavern. Within this cavern was a smaller temple, capped with a stone bust of Aita, whom the native people saw as a god.
After European explorers arrived in the Americas, various branches of the Assassin Order operating in Europe sent members across the Atlantic Ocean; their aims were to expand their Order, as well as to counter the efforts of their enemies, the Templars. Seeing that their Creed was similar to the ideals of the native people, the Assassins united with several local Mayan, Aztec, and Taíno tribes. Tulum eventually became the largest Assassin settlement in the region, and was used as their local base of operations.
In 1673, the Caribbean Mentor Bahlam was able to rescue the Sage Thom Kavanagh from the Templars' clutches, and brought the man to Tulum to rest and focus on the Observatory. After telling Thom of the secret war between the Assassins and Templars, Bahlam and his son Ah Tabai saw Kavanagh off as the Sage set sail for the hidden Observatory.
Exposed to the Templars
By 1713, Ah Tabai had taken his father's place as Mentor of the Caribbean Assassins, and trained many Assassins, including Mary Read and Duncan Walpole, deep within Tulum's jungles and temples. Unaware of Walpole's impending betrayal, Ah Tabai sent him to free the newest Sage, Bartholomew Roberts, from the Templars in 1715. However, the pirate Edward Kenway and his fellow pirates were attacked by Walpole's ship. After killing Walpole and using his identity in an attempt to earn a reward, Kenway unwittingly carried out Walpole's betrayal, selling the location of several Assassin bureaus to the Templars, including Tulum.
A year later, when Kenway had finally arrived at Tulum and met the Assassins, the Templars launched an attack on the stronghold. Led by Laurens Prins, slavers stormed the settlement, killing or imprisoning most of the population, along with Edward's crew. However, Kenway and Read were able to free many Assassins and pirates, driving the slavers from Tulum.
Relocating to Great Inagua
For the next six years, the Templars used both the English and Spanish navies to relentlessly attack Tulum. After Kenway allied himself with the Assassins, he helped to repel one last onslaught before setting out to eliminate the Templars in the region. After killing Grand Master Laureano de Torres y Ayala, Kenway offered his island hideout on Great Inagua to Ah Tabai. Knowing that Tulum would continue to be a Templar target, the Mentor accepted Edward's offer, although the Assassins continued to use Tulum as a base of operations.