|Rank||Fourth Rank Archineer|
|First appearance||Day 1|
Isaiah is a Archineer of Antonia. Little is known of his past, other than that he joined the Archineers at a young age. He, along with most of the Archineers, took on a combat role at the beginning of the Second Clockwork War. Chief Archineer Kenan deployed Isaiah and a squad of Kingdom Force soldiers to the western shores to investigate abnormal Source Well activity. They were ambushed by Clockworks, and only Isaiah managed to escape. Though he was badly injured, he found Lock and Emi and warns them about the coming invasion before collapsing. Emi goes to the village of Seacrest Shores to get help while Lock fends off a clockwork scouting party.
In the confusion, Emi disappears. Isaiah guides Lock in defending the village from the Clockwork army while Lock's grandfather, Tobias, evacuates the villagers. Isaiah, Lock, and Tobias flee to a nearby Kingdom Force outpost, Northshore Fort, where they protect an incoming Source shipment. Afterwards, Isaiah takes Lock to Antonia to join the Archineers' fight.
After joining the Archinners, Lock and Isaiah part ways and are deployed to seperate fronts. Their paths do cross occasionally, even fighting side by side a few times. Isaiah was present during the second meeting Lock had with Lord Agony at Ironfist Quarry and the Final Battle at Antonia Gates. Although he is never given a definite ending, he is last seen alive and well at the end of the game.
At Ironfist Quarry Isaiah teams up with Lock and becomes an invincible in-game ally. Though he cannot repair turrets he helps fight Clockworks. In the final battle against Agony, Isaiah appears again with Heathern to assist Lock in defending Antonia and defeat Agony once and for all.