For canon information, see the Mass Effect wiki page for Tortuga. This page is for CDN members' non-canon additions.
Tortuga is an inhospitable garden planet situated in the Nemean Abyss. It is known both for its harsh planetary conditions and its ruthless inhabitants: pirates, slavers, drug lords and other notorious denizens of the most lawless parts of space.
"Tortuga" is what humans call the planet, likening it to an ancient Terran sea pirate port of the same name.
Tortuga has a nitrogen-oxygen atmosphere, notably more dense than Earth's, but lacking natural hazardous chemicals. Most toxins present in the planets are products of industrial contamination or local warfare. The air, depending on the location, is either scorchingly arid or extremely damp. It is always befouled by copious amounts of fine brownish-yellow dust from the planet's great sandstorms. This dust creates a global yellow haze, making the sky perpetually half-shrouded and sickly yellow. The amount of dust in the atmosphere gives the day side of Tortuga an almost homogenous appearance when viewed from space, just a dull mustard-colored sphere. On the night side the lights of large settlements are still quite visible. The dusty haze creates a perpetual natural "nuclear autumn", sheltering the surface from the blistering heat of the local star, as well as smoothing out the thermal cycles, making the temperature difference between day and night only dramatic instead of truly hellish.
The planet appears to be extremely arid, covered by one huge desert, giving it a lifeless look. This is not the case. Tortuga is a garden world with significant resources of fresh water, if mostly underground. While the planet lacks real forest, it has enormous steppes covered with a dense carpet of dully colored vegetation, mostly in form of large lichen, grass and short bushes. There is a number of wide shallow silty seas, but rivers and fresh water lakes are exceedingly rare. A significant portion of the planet's biosphere is hidden from view, living underground, in the soil itself and in extensive systems of tunnels and caves. Even under the most lifeless desert regions, featuring barely anything more than microbal life, a whole microcosm of biota can be hiding. Tortugan biosphere could be a boon to the xenobiological scientific community, but local "sociopolitical climate" makes most research endeavours unaffordably risky.
The desert regions of the planet dominate huge parts of the surface, especially in the equatorial regions. Great plains of brown or yellow sand seem stretch over thousands of miles, with occasional small volcanoes or mining settlements being the only landmarks. Some local batarians call Tortuga "Camala's evil twin" sometimes. Lack of large mountain chains, expansive plains and a dense atmosphere create incredibly violent sandstorms capable of leveling cities of insufficiently sturdy buildings. Such cases are unheard of and were notoriously common during the early settlement of the planet. Direct exposure to Tortugan sandstorms is lethal. Not only the wind itself is violent, it is densely packed with sand grains, ranging from fine silica dust to sharp crystalline grains. It works like a sandblasting machine, obliterating non-reinforced clothing is moments and causing terrible trauma to any species, violently shaving off skin and potentially destroying flesh down to the bone. People travelling over the regions where sandstorms are common use special reinforced and hermetically sealable vehicles. Installing turret hardpoints on vehicles is also common, due to both the pirate threat and the fact that steppes and deserts of Tortuga are home to some extremely dangerous predators, some of them are on par with those of Tuchanka and Eingana in terms of danger to sapients. A six-limbed apex predator of Tortugan desert known as "nmask" is a prime example.
Tortuga could easily be called a planetary version of Cartagena station. The planet is heavily colonized, with settlements, industrial complexes, paramilitary fortifications, mining sites and transport arteries dotting the surface. There is no singular government on Tortuga, power is divided between numerous city states and various smaller groups. Order is maintained by a balance of power between local paramilitary groups and hired security forces, and this balance is shaky at best, occasionally erupting into localized conflicts of various magnitude. Besides squabbles between the mercs and industrial competitors, piracy and slave grabs are common on the planet, leading to the unsurprising fact that everyone carries weapons and combat omnitool modules.
The local market has everything, from food to weapons, from spices to drugs and from second-hand (usually stolen) ships to slaves, often caught on the very planet they're being traded on. There's no real black market on Tortuga -- the entirety of local trade is one huge black market all by itself, if the term is even applicable in the Nemean Abyss. A newcomer unfamiliar with local rules and unspoken laws is in constant danger, and not all are capable of adapting to local society. Those civilians who manage to fit in often lead rather regular and even civil, if still risky, lives. In the calmer parts of the planet it is not uncommon to see a pirate, a drug dealer, a hydroponics agroengineer, a street thug and a miner to drink in the same little bar without any problem whatsoever.
Tortuga has become home to almost all known species, including a large number of individuals from smaller and less known ones from the Terminus and the Abyss. The shakiness of local peace leaves little place for petty racism, most conflicts are over much more practical matters. For example, Tortuga, like many Nemean worlds, has a large batarian presence, but that never managed to discourage humans from settling there alongside the "blinks" and even starting joint businesses. On Tortuga, one is much less likely to be beaten on racist motivations than to be mugged for cash and tech.