Source of all living matter (Anime)

"Long, long ago...before anything besides inert matter existed in this universe, all manner of insignificant things came into and out of being. Eventually, something survived. We call that thing "life.""

- Zeke Jaeger explains the origin of life

The "source of all living matter" (有機物の起源) is the tentative name attributed to the anomaly which granted Ymir Fritz the Power of the Titans almost two thousand years ago. It was the source of both the Power of the Titans and the abilities of the Founding Titan.

Properties
While it is unknown whether or not the anomaly was indeed the origin of all life on Earth, it was evidently capable of dramatically affecting organic life in its immediate vicinity. A tree which stood over the anomaly in ancient times grew to immense proportions compared to those surrounding it. Physical contact between Ymir Fritz and the anomaly caused the creation of the Power of the Titans and subsequent connection of living and dead consciousness in the Eldian race through the Paths. After emerging from the neck of Eren Jaeger's Founding Titan, the creature is very animalistic in nature, its only goal being to reconnect with Eren's head. This is shown by its constant squealing and thrashing when in distress. It is also incredibly fast despite its tiny limbs.

History
While fleeing from her Eldian tormentors, Ymir Fritz encountered the life-giving anomaly beneath a colossal tree in the wilderness. Upon physical contact, she was imbued with the Power of the Titans, gaining the immense form of the Founding Titan.

Return to Shiganshina arc
In his journals, Grisha Jaeger recounts his conversation with Eren Kruger in which Kruger elaborates on the varying stories surrounding Ymir and the origin of the Titans. While some consider Ymir's power to be of the Devil and others believe her power was a gift from God, Kruger notes that some believe the origin of Ymir's power was the "source of all living matter", though he admits all explanations of such history are ambiguous and ever-changing.

War for Paradis arc
While attempting to come into contact with Zeke Jaeger to unlock the power of the Founding Titan, Eren is decapitated by Gabi Braun shooting him in the head with an anti-Titan rifle. Regardless, contact is still achieved and sends the consciousnesses of the two brothers into the paths with Ymir where Eren witnesses the origin of Ymir's power. Upon gaining control of the Founding Titan moments after decapitation, the anomaly manifests from Eren's body and reattaches itself to his head, saving Eren from completely dying.

As anticipated, the anomaly manifests out of the spine of Eren's Founding Titan after Jean Kirschtein decapitates it with explosives, this time on a much larger scale. The colossal anomaly attempts to enter the Founding Titan's severed head but is stopped by Reiner Braun's Armored Titan. Reiner holds the anomaly in place while Armin Arlelt transforms into the Colossal Titan, enveloping both Reiner and the anomaly in its explosive transformation.

The anomaly survives the detonation while Reiner and Armin move toward it in an attempt to kill it. However, another explosion reports from the crater behind them, where Eren reemerges in a new Titan body. Armin moves to face him, leaving Reiner to deal with the "shining centipede." The serpentine being then begins to exude a large amount of gas as it continues writhing, billowing towards the top of Fort Salta. The assembled soldiers quickly determine that this gas is similar to Zeke's spinal fluid cloud, used to turn the inhabitants of Ragako into Titans. Shortly after, the remaining Eldians are transformed into Titans which leap off the mesa, rushing to defend the anomaly. Sensing Eren nearby, the anomaly makes a beeline for him in an attempt to reconnect with his head, now with an army of Pure Titans following suit. Knowing that it must not make contact with Eren, Reiner stands in the creature's path and and attempts to restrain it. Barely managing to hold on the squealing centipede, Reiner is quickly set upon by the horde of pure Titans, which try to pull him away from the anomaly. Annie Leonhart and Pieck Finger transform of their own will in order to engage the creature and assist Reiner, but even that proves insufficient as they are also set upon by the Titan horde.

Before they can be torn apart however, Mikasa Ackerman kills Eren, resulting in the Power of the Titans vanishing, permanently turning all Titans back into humans. This also causes the anomaly to die and dissolve away into steam.

Trivia

 * The "source of all living matter" bears some resemblance to , an ancient species of aquatic lobopodian worm from the Cambrian period.
 * When Zeke Jeager talks about the origin of life on earth the entity can be seen forming and changing shape in the ancient ocean.
 * The entity itself displays many traits that Zeke associates with “life” such as adapting, changing its form, seeking to multiply.
 * At the end of the series the tree under which Eren's head was buried is shown to have grown to resemble the one where Ymir Fritz stepped inside and met the "source of all living matter" before being turned into the first Titan.