Ruom

Ruom was a protoss zealot.

He was assigned to the isolated Protoss Advance/Experimental Facility (PAX), known for their cutting edge scientific research and their willingness to go beyond ethical boundaries. He and two other zealots were assigned to independently observe an experiment devoted to destroying the creep. To this end, PAX had infected it with a virus.

He and fellow zealot Goluroth were observing a sample when the creep suddenly grew over the two of them. Goluroth severed his psionic appendages and killed himself, while Ruom fell into catatonia, his mind filled with disturbing images. He was put into an isolation cell.

Infestation
While in isolation, Ruom transformed into an infested protoss, and set about "fogging" the Khala, causing visions of previous unethical experiments among the protoss scientists and driving them mad.

One scientist sabotaged the facility's gate, cutting it off from the rest of the protoss before cutting off his own psionic appendages and killing himself.

Ruom eventually flew into combat, still using his psionic blades against the remaining protoss, killing all but one scientist, Gruu. The latter fled to the chamber holding the creep, overloading the temperature regulation mechanism and freezing the entire facility.

The abandoned facility was later discovered by a terran military expedition. They found the mutated creep to still be alive...