The bio-bomb was a prototype device created by Crimson Base. It was designed to secrete a 'carnivorous atmosphere' which would eat all carbon-based objects, including all living beings. Non-carbon objects like concrete or plastic remain untouched, leaving most real estate undamaged. The exception would be things made of wood or cotton such as upholstry, paper and some floors.
It was used despite not being perfected when Crimson recieved word of the terrorist attack on Pelvanida. The bio-bomb turned out to work too well; its area of effect turned out to be much greater than expected, and the entirety of Las Vegas (including Crimson Base itself) was consumed.
Only five known individuals survived the bio-bomb. James Zanasiu, Ender McThair, and Ken were Pelvanida personnel warned beforehand and so wore protective chemsuits. Dragore Wing, a Pelvanida experiment, was kept alive by regenerative nanobots while constantly being eaten alive by the atmosphere. The pain drove him insane and his eventual fate is unknown. A civilian, Tardigan, survived simply by being a water bear, though he was driven insane by witnessing everyone he'd ever known eaten alive in front of him.
Six months later, while trying to escape the quarantine zone, James and Ken stumbled across an earlier prototype bio-bomb. Unlike its successor, it had a virtually unlimited spread radius. Tardigan planned to launch it out of the quarantine zone and kill thousands. Ken sacrificed himself to prevent this from happening. (Ground One)