Threshold

Threshold was an ancient society, existing 2 billion years before humanity. They were spawned from the "Seed,"^[3] which contained the genetic material of the massacred Genoshan mutants, sent to the past by the present-day mutants.^[2] Their governance was reborn as two houses, one called equally from each generation of Enriched (mutants), the other drawn from Enshrined (humans).^[1]

Having evolved into a thriving society, Threshold was attacked by the prehistoric Shi'ar, but the Thresholders slaughtered them. When the Shi'ar returned with an army, Threshold answered with five heroes and once again slaughtered the Shi'ar forces in an event called the First Blood Spilled.^[4]

Later, Threshold warred with its rival, the Unbreathing, an industrial anaerobic society. After losing the first Oxygen War, the Unbreathing attacked again with even deadlier tactics, so Threshold created the sentient bacteria Sublime and Arkea, let them parasite in Thresholders bodies. However, the bacterias quickly became self aware, they turned on Thresholders and then each other, causing the downfall of Threshold.^[1]

Upon hearing this story from three resurrected Thresholders—Amass, Crave, and Theia—in the present, the Marauders went to the past to try to save Threshold. However, they jumped to the period when Arkea and Sublime had already begun to take over.^[5] Cassandra Nova offered herself to both Arkea and Sublime, then lobotomized all of them at once, saving the Thresholders from the bacteria siblings.^[6]

However, the threat from the Unbreathing remained, who were fighting for their own survival. Under the command of Commander Nightfount (Stryfe), they plotted to wipe out all oxygen breathers with their Oxygen Ignitor, except Stryfe himself.^[3] The Marauders were reluctantly forced to depart, leaving the Thresholders to face the threat alone, but they stranded Cassandra Nova there as Kate Pryde wanted revenge for Cassandra's massacre of Genosha, including Pryde's father. Some time after this, the Thresholders died, but one of them, Grove, survived under a new name and form: Okkara.^[6] The insectoid Xilo was another survivor.^[7][8]

Back in the present, Pryde was disappointed that she could not save Threshold nor Genosha, but she soon realized that Threshold's existence was in a causal loop. Pryde went to Genosha, assembled a mutant circuit to which they would place genetic material from the millions of dead Genoshans into Kate's mysterium box ("the Seed"), then sent it back in time to give life to the Thresholders.^[2]

• According to the writer Steve Orlando, the surviving Thresholders, Okkara and Xilo, regrew themselves out of almost nothing so they may not have retained any memories of Threshold. "Their minds may have returned, but what's healed may be more like a blank slate."^[8]

• The Thresholders' clothing came from amoebas.^[5]
• The Thresholders were born in a birthing sea.^[1][3]
• Threshold's story seems to take place during the Great Oxidation Event, when anaerobic life (represented by the Unbreathing) were being killed off by the rise of oxygen.