Archimedes concluded that there were multiple xel'naga ruins on Aridas. However, the military situation had turned dire against the Aridians, especially since a zergcerebrate had somehow taken control of a protoss tribe using xel'naga technology. Archimedes wanted to capture it for further study, but this would not prevent the zerg from fighting the terrans.
Archimedes was exploring a huge cavern beneath excavation sites when he was captured by the zerg. They surrounded his science vessel with minions. He was able to contact the Dominion forces and request a rescue, which was successful. Archimedes told the Dominion commander he would let the emperor know of his courage.
Archimedes located the Argus stone on the far side of Aridas, protected by numerous protoss tribes. The protoss, in a last-ditch effort to protect and use the stone, placed it within a temple they had warped in from Aiur, which would focus the energies of the stone. Archimedes' forces shattered the temple, defeating the protoss. Archimedes picked up the stone, putting it on his science vessel.
In an effort to recover the stone, the Zerg Crusaders destroyed Archimedes' battlecruiser escort, then pursued him through multiple Dominion bases. The zerg captured some of his allies, infesting them in order to gain information on Archimedes' whereabouts. The zerg eventually stole the stone from Dominion forces.
Reduces the hit points of biological units near the targeted unit (and the targeted unit itself if it is biological) by 250 over 30 seconds. Mechanical units are immune, but biological units passing near an irradiated mechanical unit will still be affected.