A vehicle-mounted heavy crossbow platform that fires 1-meter steel bolts weighing 5 kilograms at velocities sufficient to penetrate reinforced concrete walls. The Arbalest uses a hydraulic draw mechanism that charges a bank of torsion springs generating 400 kilograms of draw force, combined with a short electromagnetic acceleration stage that brings the bolt to terminal velocity. The weapon is mounted on a powered gimbal that allows 180-degree traverse and 45-degree elevation from a vehicle roof or fixed position.

Ouroboros developed the Arbalest as a breaching tool for tactical teams that need to penetrate fortified positions without explosive ordnance. A 5-kilogram steel bolt arriving at 200 m/s punches through walls, doors, barricades, and light vehicles with the kinetic energy of a small cannon round, but without the explosive signature, fragmentation hazard, or ammunition regulation of conventional heavy weapons. Like the Longbow, the Arbalest exploits the legal fiction that anything firing a bolt is a crossbow.

The weapon's most common deployment is punching access holes through walls during forced-entry operations — a single Arbalest bolt creates a 15-centimeter breach that operators can use as a firing port, observation point, or anchor for breaching charges. Three bolts in a triangular pattern create a hole large enough for a person to enter. The process is slower than explosive breaching but creates no blast injury risk to occupants the entry team wants alive.