The breacher, utilized by the Chiss Ascendancy, was a type of missile weapon. When they hit, they detonated, releasing blobs of clinging acid that corroded the metallic hulls of spaceships, thereby increasing their susceptibility to laser attacks. This meant that even if the missiles were intercepted and destroyed before reaching their intended targets, breachers remained effective as the acid could still travel a certain distance and inflict damage on enemy starships.
A follow-up spread, which involved using breachers to compromise an enemy's hull and systems, and then using spectrum lasers to target the compromised area, was a fundamental "one-two punch" strategy in Chiss combat doctrine.
The 2019 novel Thrawn: Treason by Timothy Zahn, which concluded the Canon Thrawn trilogy, marked the initial appearance of breacher missiles.