First Strike - Cortana 4

She generated several hundred thousand Covenant codes in a microsecond and cracked the system. She diverted the air vents along the corridors the Chief and his team occupied to the primary air systems. She then tasked the processor pumps to ser- vice the rest of the ship and activated them—in reverse.

 Warnings flashed throughout the Covenant system as the pressure suddenly dropped in 87 percent of the ship's passages. She squelched them.

 The other presence in the system tried to shut the pumps off. She blocked that signal and assigned a new code to the security systems: "WE REGRET TO INFORM YOU."

 She heard the other AI scream, an echo of an echo that rever- berated through her processors. She knew the sound—familiar like a human voice, but terribly distorted.

 She scanned through the ship's cameras and saw Grunts squeal and fall over, methane leaking from their breathers as the pressure dropped. Engineers turned blue, slowed, and died, floating in place with tentacles twitching, still searching for something to fix. The Elite hunt-and-destroy parties halted in the corridors and clutched their throats, mandibles snapping at air that was no longer there; they toppled and suffocated.

 An impulse flickered through her ethics subroutine and gen- erated an interrupt command, designed to make her stop and re- think her decisions. But Cortana knew it was either kill or be killed. She rerouted all signals from her ethics routine and shut it down. She couldn't afford to be slowed down by such secondary considerations.

- Halo: First Strike, Chapter 7