Thorian

The Thorian, also called Species 37, was an ancient sentient plant at least fifty thousand years old that dwelt beneath the surface of Feros. A unique creature with mind-controlling and telepathic abilities and a vast sensory network, it released spores that let it control any who inhaled them, binding them as thralls. It described itself as "The Old Growth." Concealed beneath the colony of Zhu's Hope, the Thorian held most of the colonists in its grip until the rogue Spectre Saren Arterius sought it out, and Commander Shepard ultimately destroyed it in 2183.

Nature#

The Thorian was, according to the ExoGeni VI, essentially "a weave of tendrils" that covered much of the surface of Feros, with some sensory tendrils kilometers long, gathered in places into nerve bundles or neural nodes distributed throughout the ruins. Though it was intelligent, it regarded other sentient beings only as potential thralls. It controlled living minds by releasing spores into the air; anyone who inhaled them came under its influence, and the creature used pain to compel obedience. Those it controlled became thralls who tended the Thorian and obeyed its will. The initial conditioning was painful, and any thrall who resisted suffered until they were conditioned against rebellion, but the Thorian did not force its thralls into danger or self-harm. The ExoGeni VI likened its care for them to that of a craftsman who is careful not to damage his tools. Its true form bore little resemblance to a plant, appearing instead as an enormous organic mass, and its lair reportedly smelled of rotting compost.

In Prothean times#

The Thorian existed on Feros long before the Protheans arrived. It spent thousands of years in hibernation, then woke for a few frantic centuries of activity before resting again. When the Protheans came and began building the metropolis that would eventually cover Feros, the curious Thorian studied them, likely took several as thralls, and absorbed them after death so that they became part of its expanding consciousness. In this way its mind gradually absorbed the knowledge that would form the Cipher, a body of understanding tied to Prothean thought. The Thorian survived the cataclysm that destroyed the Protheans and went on growing across Feros for the next fifty thousand years.

The colony at Zhu's Hope#

In the late 2170s the ExoGeni Corporation began settling Feros, establishing the colony of Zhu's Hope in one of the ruined skyscrapers, unaware that the Thorian's lair lay deep below it. The great plant had awakened from hibernation, and the presence of so many potential thralls so close was too tempting to resist. In 2183 a small survey team exploring the ruins inadvertently entered its lair and was infected with spores. ExoGeni realized what had happened but, instead of protecting its colonists, isolated the settlement to observe the creature's sensory and mind-controlling potential. It took less than a month for around eighty-five percent of the inhabitants of Zhu's Hope to fall under the Thorian's control and begin performing tasks for it. The colonists were permitted to pantomime a normal existence until the Thorian needed them, though a few, such as Ian Newstead, were strong enough to resist for a time, and the creature kept these out of sight.

Saren and the Cipher#

The rogue Spectre Saren Arterius learned of the Thorian's existence and its connection to the Protheans. He traveled to Feros in secret with a contingent of geth and a powerful asari biotic, Shiala. Saren negotiated a trade, offering Shiala as a sacrifice; she melded with the Thorian, and sharing its consciousness gave her the Cipher, which she then transferred to Saren's mind. Unwilling to risk Commander Shepard, who was in pursuit, gaining the same knowledge, Saren ordered the geth to destroy the Thorian and erase all trace of it. The geth assaulted Zhu's Hope, but the enthralled colonists blocked the entrance to the lair and fought to the death to defend the creature. News of the attack reached the Normandy, and Shepard arrived to investigate.

Destruction#

At first the Thorian saw Shepard as the perfect instrument to destroy the geth without risking another betrayal, and it had the colonists welcome the squad and urge them to focus on the synthetics. After Shepard learned the truth at the ExoGeni building, the creature turned the colonists against the squad, even sending them to attack the Normandy, and made a final attempt to stop the team through the colony's leader, Fai Dan, who instead rebelled against its control and shot himself. Underground, Shepard confronted the Thorian itself, which produced a clone of Shiala to speak for it. Calling itself the Old Growth and dismissing humans as "meat, good only to dig or decompose," it sent clones and Thorian Creepers against the squad. Shepard destroyed the neural nodes distributed throughout the building, dislodging the Thorian and sending it plunging through the ruins to its death. Shiala, freed from its hold, was almost saddened by its end, recognizing it as a unique form of life that would never be seen again.

Aftermath and legacy#

Even after the Thorian's death, the spores continued to affect its former victims, who suffered headaches and muscle spasms reminiscent of their time under its control. Shiala, if spared, was left with green-tinged skin like her clones and unstable biotic abilities, and Zhu's Hope sought outside help to study and cure the affliction. Years later, when the Reapers attacked the colony during the great war, the lingering hive-mind effect of the spores allowed the colonists to coordinate effectively and hold against the invaders long enough to evacuate. Scholarship also noted the Thorian's singular nature: a datapad belonging to Dr. Garret Bryson, compiled during the search for Leviathan, reasoned that the Thorian was unique because it had developed without mass relays or Reaper technology, depending solely on organic tools, and compared it to Leviathan as another creature that had survived by such means across vast spans of time.