The Ssi-ruuk, pronounced /'si ruk/, with the singular being Ssi-ruu, were a reptilian species that launched an invasion from the Unknown Regions into the galaxy, triggering the Invasion of Bakura in 4 ABY, shortly following the Battle of Endor. This species depended on a technology known as entechment, which involved extracting the life energies of sentient beings to use as power sources for their mechanical devices. They possessed a substantial war fleet and governed an empire called the Ssi-ruuvi Imperium within the Ssi-ruuk Star Cluster situated near the galaxy's edge.
Ssi-ruuvi society was highly structured, characterized by a strict caste system determined by skin color, which indicated an individual's socio-economic status. The majority of Ssi-ruuk exhibited xenophobia towards other species, stemming from their stringent religious beliefs and the compartmentalized nature of their society. Due to the isolated location of their home territory in the Ssi-ruuk Star Cluster and their religious apprehension about dying on an unconsecrated world, few Ssi-ruuk ventured beyond their Star Cluster. Consequently, they remained largely obscure to the rest of the galaxy, with limited interaction with outsiders even during the eras of the New Republic and the Galactic Alliance.

The Ssi-ruuk were a sizable bipedal reptilian species that also displayed avian characteristics. They moved on two powerful legs at the rear, maintaining balance with a strong tail and two upper limbs ending in three prehensile claws. Despite being reptilian, they were actually warm-blooded. A typical adult stood between 1.9 and 2.2 meters tall (roughly 7.2 feet) and weighed approximately 350 kg (~770 pounds). They were known for their impressive physical strength, comparable to that of an average adult Wookiee. The species possessed remarkable grace and speed for their size. Their skin was thick enough to withstand blaster fire, sustaining only minor burns. The large bodies of adult Ssi-ruuk were covered in glossy scales that ranged in color from brown to turquoise. They had long, beak-like snouts containing sharp teeth and used their talons to kill prey, as they were naturally carnivorous.
Regarding eyesight, Ssi-ruuk were highly sensitive to light, leading them to have triple eyelids to shield their vision from sudden bright flashes. Their large black eyes, typical of reptilian species, suffered from poor eyesight. The unique structure of their eyelids significantly reduced their susceptibility to being blinded by sudden light. However, the species did not rely solely on their eyes like Humans. Instead, they utilized a keen sense of smell, enhanced by two forked "tongues" that extended from their nostrils. This acute sense of smell allowed them to discern the emotional state of others based on scent changes, enabling Ssi-ruuk to "read" individuals. These olfactory sensory organs, commonly known as "scent tongues", were black and flickered out when in use. This occurred only when a Ssi-ruuk was familiar with a being's "scent", allowing them to detect deception and making it difficult to lie to them. However, they found the scents of other species unpleasant. Their own odor was described as strong and acrid, with a distinct reptilian scent.

The Ssi-Ruuvi language consisted of a series of musical tweets and whistles. This intricate language employed bird-like honks, whistles, growls, and throat clicks. Some of the higher pitches in the Ssi-ruuvi vocabulary were beyond the range of human hearing. Ssi-ruuvi chord-phrases could convey a significant amount of information in just a few notes. It was believed that species like Humans were either unable to speak their language or found it extremely difficult because their mouths were unable to produce the necessary sounds. When a Human did attempt to speak Ssi-ruuvi, native speakers perceived it as a halting and stuttering version of their own language. Instead of wearing clothes, they used bandoleers to carry tools, weapons, and other equipment. They found the concept of covering the body with clothing amusing and therefore did not wear anything that would conceal their thick, scaly hides.
The average lifespan of a Ssi-ruu ranged from 100 to 120 standard years, although members of the ruling hierarchy lived much longer. Children were considered to be between 1 and 5 years old, while young adults were between 6 and 10 years old. Adults ranged from 11 to 55 years of age. A Ssi-ruuk reached middle age between 56 and 90 years old, and old age from 91 to 115 years old. Ssi-ruuk older than 116 years were regarded as venerable elders.
It was believed that there were no Force users among the Ssi-ruuk, as they were inherently blind to the Force.
The Ssi-ruuvi Imperium had two primary centers of power: the Conclave, representing the religious authority, and the Elders' Council, representing the political authority. These two bodies often competed for control of the empire, and only the leader of the Imperium could prevent civil war. The leader of the Imperium was known as His Potency the Shreeftut and held supreme power over the Ssi-ruuvi Imperium. The two councils served as advisory bodies to the Shreeftut. Ssi-ruuvi society was largely clan-based, deeply rooted in tradition and family history. Clans were led by patriarchs, and charismatic individuals could command multiple clans. Control over a large number of clans earned patriarchs considerable respect from their peers.
Similar to the long-extinct Sith species, Ssi-ruuvi society was structured by a strict hereditary caste system. However, unlike the Sith, the Ssi-ruuk caste system was based solely on skin color. The system consisted of six main groups: blue, gold, yellow, red, black, and green. A Ssi-ruuk's skin color symbolized their socio-economic standing within society. Each Ssi-ruuk was predominantly one color, and mating between different colored Ssi-ruuk was forbidden. Offspring from mixed unions were brown-hued and considered illegitimate, relegated to the lowest and most menial positions in society. Additionally, a related species known as the P'w'ecks was considered inferior and used as slaves.
The known castes included:

- Blue: Representing the noble caste [6], Blue Ssi-ruuk were the politicians and leaders of Ssi-ruuvi society, holding most political positions and dominating the executive Elders' Council, which administered the Imperium. They were distinguished by their blue scales, smaller size, and longer tails. As the highest caste, they received the most honor and praise. They were generally perceptive and ambitious. An example of this caste was Sh'tk'ith , commonly known as Bluescale. [7]
- Gold: Gold Ssi-ruuk formed the religious caste of Ssi-ruuvi society. They were few in number and stature but dominated the Conclave, which focused entirely on religious affairs. Gold Ssi-ruuk also performed religious ceremonies like the Consecration Ceremony, which "consecrated" foreign planets for annexation by the Imperium. [7] [8]
- Yellow: Yellow Ssi-ruuk studied sciences and operated the technology used by the Ssi-ruuvi Imperium. [8]
- Red: Red Ssi-ruuk comprised the military caste. These Ssi-ruuk were typically broader and stronger than other Ssi-ruuk and possessed a predatory nature. They also had the ability to remain undetected when alone or in pairs. An example from this caste was Admiral Ivpikkis, who commanded the first invasion of Bakura. [7] [8]
- Green: Green Ssi-ruuk were the most numerous caste. This caste was the lowest that still received respect. They never held positions of power but staunchly supported the caste system as workers. [1] [8] [9]
- Black: Very rare, they worked as assassins and espionage agents for the Imperium and were honored among other Ssi-ruu tribe members. [9] [8]
- Brown: Brown Ssi-ruuk were considered outcasts because they were the offspring of Ssi-ruuvi from different castes. Since class intermarriage was strictly prohibited, many were killed at birth. They performed the most menial jobs. It was commonly believed that they were the ancient ancestors of the P'w'ecks. According to the G'nnoch, the birth of a multi-colored Ssi-ruu known as the Keeramak would herald a popular uprising by the oppressed brown Ssi-ruuk and P'w'ecks. The Keeramak was born following the punitive Chiss/New Republic incursions around 4 ABY. [9] [8]

Ssi-ruuvi culture was significantly influenced by two main factors: their speciesism and their religious beliefs. These factors led them to believe that they were physically, mentally, and spiritually superior to all other races. Consequently, they viewed themselves as inherently better than all other species, which they considered inferior. Culturally, the Ssi-ruuk displayed a speciesist attitude toward other species, deeming them suitable only for slavery and entechment, a process that utilized the life energies of sentient beings as a power source for their mechanical technology.
This attitude affected their interactions with other sentient species, ranging from their lesser saurian P'w'eck cousins to the advanced mammalian Human and Chiss civilizations. As a result, the Ssi-ruuk aimed to conquer and subjugate other civilizations to exploit their labor and resources. The majority of Ssi-ruuk dedicated their lives to preserving and expanding their Imperium, even at the cost of subjugating other races. Consequently, relations between the Ssi-ruuk and neighboring powers like the Chiss Ascendancy, Galactic Alliance, and the Yuuzhan Vong were virtually non-existent by 28 ABY. However, they did not share the same genocidal beliefs as the Yevetha of the Duskhan League during the Yevethan Purge and Black Fleet Crisis.
Their speciesism was justified by their strong religious beliefs. According to their sacred text, the G'nnoch, four eggs were formed at the universe's creation. From the first hatched Ssi and P'w'itthki, the progenitors of the Ssi-ruuk and P'w'eck species, respectively. Ssi's children hatched from the second egg, while P'w'itthki's children hatched from the third egg. The fourth egg was reserved for Ssi-Ruuk who earned a place in the afterlife. Ssi eventually fought and defeated P'w'itthki, allowing P'w'itthki's hatchlings to live on the condition that they serve Ssi's children for eternity. This myth explained the origin of the relationship between the Ssi-ruuk (Ssi's hatchlings) and the P'w'ecks (P'w'itthki's hatchlings) and their concept of supremacy over all other sentient species.
A significant concept in Ssi-ruuvi culture was the belief in souls and an afterlife. Most Ssi-ruuk highly valued the souls of their own kind and believed that if a Ssi-ruu died on an "un-consecrated world," their soul would be denied access to the fourth egg, the Ssi-ruuvi afterlife, and would wander the universe alone. This was considered a horrifying fate. As a result, most Ssi-ruuk avoided direct combat when away from their homeworld. This belief explained why the Ssi-ruuk rarely traveled into the galaxy and remained in their star cluster. However, resources began to dwindle in their isolated space, forcing them to expand their Imperium into the fringes of the known galaxy by 1 BBY. To compensate for this disadvantage, the Ssi-ruuk used large numbers of droids and P'w'ecks, a smaller species enslaved by the Ssi-Ruuk, to aid them in their fleets. Around that time, Emperor and Dark Lord of the Sith Palpatine contacted the species through the Force, offering them dozens of worlds and millions of humans to entech in exchange for the use of Ssi-ruuvi entechment technology.
Priests would conduct an hour-long ceremony to consecrate a conquered planet, dedicating it to the Ssi-ruuvi Imperium and giving it a Ssi-Ruuvi name. The planet Bakura was consecrated as Xwhee as a prelude to an invasion in 28 ABY.
A lesser-known Ssi-ruuvi religious concept was the prophetic coming of a multi-colored Ssi-ruu whose arrival would overturn Ssi-ruuvi society. This prophecy was fulfilled with the birth of the Keeramak. However, the Keeramak was merely a tool of Yuuzhan Vong infiltrators who had infiltrated the weakened Imperium between 4 ABY and 28 ABY following its defeat by the Alliance of Free Planets and the Galactic Empire at Bakura during the Invasion of Bakura in 4 ABY. In 23 ABY, the Imperium engineered a faux popular rising of the P'w'eck Emancipation Movement under the Keeramak to fulfill this prophecy. This plot to reconquer Bakura was thwarted by a genuine P'w'eck uprising and the death of the Keeramak.
The Ssi-ruuk language, known as Ssi-ruuvi, was composed of melodic clicks and whistles, sounding similar to a flute, which earned the Ssi-ruuvi the nickname "Fluties". Due to their unique physiology, Humans could not reproduce the language because they lacked the necessary organs. While Ssi-ruuk could speak other languages, limited contact with other species forced them to rely on translators when offworld. Ssi-ruuk traveling outside their space were often accompanied by a droid, slave, or hireling who translated for them.
The staple diet of the Ssi-ruuk and their P'w'eck cousins consisted of small fft reptiles, eaten with ceremonial knives.

One distinctive feature of their technology was the use of entechment, where a living being's life energy was electronically extracted and used as a power source for machines. Entechment powered a wide range of their technology, including starships, power stations, Ssi-ruuvi security droids, and ion paddle beamers. Although the Ssi-ruuk claimed entechment was painless, victims remained in agony during and after the process.
Even when installed into power cells and machinery, these disembodied beings remained in continuous agony until their life energies expired. Given the excruciating pain and resulting death, the Ssi-ruuk did not entech their own people, preferring to use "inferior" sentient species, particularly P'w'ecks, a similar saurian species reduced to servitude long ago. When the Ssi-ruuk attacked Bakura in 4 ABY, they discovered that Humans were a more potent energy source than P'w'ecks after taking Imperial prisoners.

By 28 ABY, the entechment process had been refined. The Ssi-ruuk had found ways to nourish the enteched souls, using life energy distilled from concentrated banks of algae and other microscopic life to prevent decay and reduce the torment felt by many enteched souls. This preserved the enteched life energy, reducing the need for frequent replenishment. The Ssi-ruuk also attempted a second invasion of Bakura, but their plot backfired when their P'w'eck slaves revolted.
Another technology unique to the Ssi-ruuk was the ion paddle beamer, their equivalent of the ubiquitous blaster rifle used throughout much of the known galaxy. These paddle beamers were unique in that their beams could not be blocked by lightsabers, as the energy would bend around the blade and strike the target. After considerable practice, Jedi Knight Luke Skywalker managed to adjust his lightsaber to block the blasts, but this change rendered the lightsaber unable to block blaster bolts.

The Ssi-ruuk originated on the planet Lwhekk, located in a remote star cluster on the fringes of the galaxy. They evolved from carnivorous animals in their jungle homeworld, gradually forming tribes based on skin color. The Blue and Gold scaled tribes were the most dominant, with the Blue scales possessing significant political power and the Gold scales establishing Ssi-ruuvi religion. These two tribes formed the Ssi-ruuvi upper class. The Ssi-ruuk eventually encountered the smaller but more numerous P'w'ecks, leading to conflict. Eventually, the P'w'ecks were subjugated and enslaved. The Blue and Gold tribes then allied and selected the first Shreeftut, creating the Ssi-ruuvi Imperium. The Blue and Gold tribes then subjugated the rest of Lwhekk and divided them into castes. The Conclave and the Elders' Council were formed, and the Ssi-ruuk expanded their empire into space. A major challenge for their race was dwindling natural resources. Their failure to develop fusion technology hampered their exploration efforts, forcing them to carry large fuel stores. Consequently, the Ssi-ruuk's initial forays beyond their home system were driven by the search for new energy sources and resources. The inability to create more efficient energy sources and dwindling resources led to the development of entechment technology. This process involved drawing life energies from living beings and placing them within technology to power it. This was applied to the P'w'eck race, whose energy was tapped to create a stable energy source. Initially, this was considered distasteful but necessary for energy production.
They eventually began settling nearby planets, expanding into their star cluster, which contained six other habitable worlds. All native races were conquered and cleansed as part of the entechment process's testing phase. Entechment of lower life forms became common, even among the P'w'ecks, cousins of the Ssi-ruu. However, it was discovered that prolonged containment of these "souls" led to madness, necessitating further expansion. Another reason was the dwindling resources in their isolated region of space. After discovering entechment, the Ssi-ruuk sacrificed countless P'w'ecks to power hordes of battle droids, which they used as part of their forces when emerging from their stellar cluster. Before this, the Imperium had never dared to expand beyond its cluster, partly due to the large distances, the xenophobic nature of the Ssi-ruuk, and their religious fear of traveling to 'unconsecrated' worlds. Due to the aforementioned lack of resources, around 100 BBY, the Shreeftut ordered the Imperium to expand, conquering a wide swath of the Unknown Regions, justifying his actions with a controversial interpretation of the G'nnoch.
During the age of the Old Republic, there were scattered references to a reptilian species encountered in the Outer Rim, but it was never determined if these were Ssi-ruu. Prior to the Rebellion era, the existence of the Ssi-ruuk was unknown to the wider galactic population.

Previously, the Ssi-ruuk were primarily concerned with external matters. However, an escalating conflict with the Chiss's empire prompted them to send exploratory missions towards the Core Worlds. The objective of this expedition was to gather "recruits" for piloting their starships. Consequently, the Ssi-ruuvi Imperium launched attacks on several isolated Outer Rim colonies before encountering the forces of the Imperial Navy. Instead of deploying the full might of the Imperial Military against these invaders, the Emperor opted to establish a clandestine agreement with the Ssi-ruuk. In exchange for their knowledge of entechment technology, the Emperor secretly agreed to relinquish control of several Outer Rim colonies to the Ssi-ruuvi, allowing them to utilize these territories as they saw fit. As 1 BBY approached, and the Ssi-Ruuk made their way to the outer reaches of the Galactic Empire, the Ssi-ruuvi's leader—the Shreeftut—experienced Force-induced visions of a hooded Human, who identified himself as Emperor Palpatine, the ruler of the galaxy. He proposed offering the Ssi-ruuvi a multitude of worlds and millions of Humans for entechment, in return for access to Ssi-ruuvi technology. Consequently, they made the decision to explore Wild Space, where they conquered the small Human settlement of G'rho, capturing and enteching many of its inhabitants. Due to their covert arrangement with the Ssi-ruuk, the Imperial leadership concealed the incident and falsely accused the Alliance to Restore the Republic of perpetrating the attack.
Among those captured was a Human boy named Dev Sibwarra, who was subjected to mind control techniques by the Elder Sh'tk'ith. They were astonished to discover that the boy possessed unusual abilities to sense others. It was through this boy that Ssi-ruuk Admiral Ivpikkis learned that Humans were the galaxy's dominant species. He also found that humanoids could be contained for extended periods when enteched, outlasting most other species. Because of Sibwarra's Force sensitivity and his capacity to communicate with fellow Humans, the Ssi-ruuk employed Dev Sibwarra to pacify the subjects undergoing entechment.
However, in 4 ABY, Emperor Palpatine met his demise during the Battle of Endor aboard the Second Death Star. With the Emperor unable to uphold his end of the bargain, the Ssi-ruuvi initiated an invasion of the outer edges of known space. They dispatched expeditionary forces targeting both the galaxy proper and the neighboring government within the Unknown Regions, known as the Chiss Ascendancy. Nevertheless, neither expedition achieved significant success: the Ssi-ruuvi barely managed to conquer the Human world of Cattamascar, and were decisively defeated at Bakura.
Similarly, despite capturing several minor Chiss worlds, the Chiss response was overwhelming and unexpected, resulting in the devastation of the Ssi-ruuvi capital, Lwhekk. Following the Chiss assault on the Imperium, a small Rebel Alliance task force arrived in Ssi-ruuvi territory. The Rebel force had come to prevent the Imperium's expansion into the known galaxy. Witnessing the Imperium in ruins, the Rebel Alliance concluded that the threat posed by the Ssi-ruuk had diminished. The Alliance pursued diplomatic discussions with the Ssi-ruuk, who found themselves unable to sustain a war on multiple fronts. These negotiations persisted for many years and extended into the New Jedi Order era, although sporadic border clashes continued. Ultimately, diplomatic relations remained strained due to the Ssi-ruuk's inherent disdain for other species.

More than two decades passed before the Ssi-ruuvi had sufficiently recovered to contemplate resuming their expansionist ambitions. During this period, the Ssi-ruuk made advancements in preserving enteched souls. Two significant events transpired during this time. The first was the birth of the Keeramak, a momentous occasion in the Ssi-ruuvi religious beliefs. The Keeramak itself, a mutant Ssi-ruu, demonstrated exceptional strategic and political acumen. The second event involved the covert takeover of the Imperium by the Yuuzhan Vong, who secretly infiltrated one of their own, E'thinaa, into a high-ranking general position. The Yuuzhan Vong possessed extensive knowledge of threats within the Unknown Regions and sought to neutralize the Ssi-ruuk early on.
Working together, E'thinaa and the Keeramak formulated a revised strategy for continuing the invasion. They forged a secret pact with the Prime Minister of Bakura, Molierre Cundertol, and orchestrated a fabricated P'w'eck slave rebellion, positioning the Keeramak as its leader. They jointly succeeded in consecrating Bakura and launching a second invasion of the planet. However, when the P'w'eck's genuinely revolted and managed to assassinate the Keeramak, all hope was lost. Cundertol himself fled back to Lwhekk, where E'thinaa executed him. The P'w'eck uprising successfully dismantled the political and religious caste system on Lwhekk, leading to the establishment of a military dictatorship under the control of the former soldier caste.
The Ssi'ruuk bear a striking resemblance to carnivorous dinosaurs. In an interview, Kathy Tyers, the author of The Truce at Bakura, revealed that the Ssi-ruuk were inspired by dinosaurs, particularly dinosaur books that belonged to Tyers's son. Tyers recounted in an interview with Ilene Rosenberg for Star Wars Adventure Journal 4 that her editor had requested five storyline concepts, and the one that Tyers favored most involved an alien menace that would necessitate a brief alliance between the Rebel Alliance and the Empire.
The Unknown Regions campaign guide inverts the roles of the green and red caste Ssi-ruu, asserting that the former are warriors while the latter are workers, which contradicts earlier established material.