The NI-1 is a centipede-form automaton approximately 4 centimeters in length and 3 millimeters in diameter, designed to enter the human body through the ear canal and interface directly with the auditory nerve. It moves with a fluid, peristaltic motion that produces no sound — targets do not feel it enter. The unit's segmented body is composed of biocompatible polymer over a flexible titanium spine, and each segment contains microactuators that allow it to navigate the curves of the ear canal without damaging tissue. It anchors itself to the tympanic membrane using molecular adhesion pads and extends a hairline neural probe through the membrane into the middle ear cavity.

Once seated, the Earwig can transmit audio directly into the target's perception — voices, sounds, commands that only the host can hear. It can also receive, monitoring the host's vocalized and subvocalized speech through bone conduction. The host cannot remove it without surgical intervention. Attempts to extract the unit manually trigger a defensive response: the Earwig releases a microdose of a paralytic compound that causes the host to lose motor control for approximately ninety seconds, during which it repositions itself deeper in the canal.

The psychological effect is the primary weapon. Hosts report hearing whispered instructions they cannot ignore, sounds that drive them toward paranoia and compliance, and a persistent low-frequency hum that disrupts sleep. Long-term hosts develop a dependency on the Earwig's audio feed — the silence when it stops transmitting is described as worse than the intrusion. Lazarus denies the NI-1 exists. Recovered units have been found in three assassinated political figures and one corporate whistleblower.