- Aveline: "How I've missed the bayou air. It has the scent of action about it."
- Élise: "Among other things..."
- ―Aveline and Élise discussing the bayou, 1768.[src]
The bayou's value as a trade route, due to it being linked to the Gulf of Mexico, made it one of New Orleans' most important sources of income during the 18th century. As a result, multiple factions clashed in their attempts to control it and use it to finance their own activities.
Sometime in the 1700s, Roussillon and Élise Lafleur came to run smuggling operations in the bayou. Their activities became threatened in 1766, when a dissident Assassin by the name of Baptiste became active in the region and gained a large group of followers that spread throughout the swamp, setting up various camps. Intending to take over the smugglers' operations and become a Templar, Baptiste's plans were cut short when he was assassinated by Aveline de Grandpré.
However, Templar activity in the bayou continued; Fort Saint-Jean, a fortress occupied by the Spanish, was used to house kidnapped slaves that were to be sent to a Templar work site in Mexico. Upon discovering this practice in 1768, Aveline swiftly shut it down by tracking down the mastermind behind the abductions. In doing so, she temporarily rid the bayou of Templar influence.
By 1771, Spanish soldiers, under the command of the Templar Diego Vázquez, entered the bayou and attempted to seize control of its smuggling operations once again. On the instruction of her Mentor Agaté, Aveline followed a squadron of soldiers through the swamp, using her blowpipe to silently poison a guard each time the group passed voodoo artifacts set up by Agaté. The surviving soldiers were thus tricked into believing they had been placed under a voodoo curse and fled the bayou. Following the disruption of another of Vazquez's plans, Aveline left for Mexico; her absence allowed for Vázquez's troops to recover.
As a result, when the smugglers were tasked with delivering supplies to the Patriots by the Spanish Governor of Louisiana in 1776, they found themselves obstructed by Vázquez's men. With the help of Aveline and an escaped slave named George, they nonetheless managed to reach their destination, where they met with the Patriots' representative, Hopton, and delivered the goods. Aveline's assassination of Vázquez then freed the bayou of his influence once more.
In 1777, a confrontation between Aveline and Agaté took place at the latter's hideout in the bayou. Agaté, unable to accept his failure to protect his student from the "Company Man" and paranoid that Aveline had sided with the Templars, attacked her. Aveline managed to overpower and confront her Mentor at the top of his hut, but decided to spare his life; this act lead Agaté to leap to his death, despite his student's attempt to save him.
- "Señor, perhaps you underestimate the vast, winding, expanse of the bayou [...] I need enough men to control all of it. Recruit the entire Spanish Army if you must. "
- ―Diego Vázquez in a letter to his accomplice, 1771.[src]
Containing a diverse range of trees and plant life, the bayou was surrounded by wet marshland and swamp waters, with an array of islands, varying in elevation, scattered throughout the swamp. A hostile environment, it was primarily inhabited by alligators, who had a notorious reputation for attacking unsuspecting prey from the banks or beneath the murky waters. Bobcats could also be found on the edges of the swamp.
As it was largely uninhabited, the bayou only possessed a single road, which linked up Fort Saint-Jean with New Orleans. Nevertheless, the region was home to more than just soldiers; the town of San Danje, situated in the north east, was a safe haven for escaped slaves, while an abandoned plantation in the south west functioned as the smugglers' headquarters.
As well as this, there was Agaté's hideout, a well-protected treehouse located in the south east. Aside from these however, the bayou did not possess many noteable landmarks, barring the occasional abandoned shack and a ship that had run aground on one of the islands in the east.
- French soldiers were only found in the bayou, and New Orleans, during Sequences 1 and 2. In later sequences, they were replaced by Spanish guards, as Spain had, by then, started to assert its control over the colony.
- At the top of the fort's lighthouse, it was possible to hear the sounds of a whale echo. When looking out over the lake Pontchartrain area, one could occasionally see said whale jump out of the water.
- Aveline was unable to use her Lady persona in the bayou.