Galen was a short stocky Radnoran, with curly brown hair and very muscular legs. He was a scientist and weapons engineer who lived in the years prior to the Clone Wars.
Along with his sister Curi, Galen worked in a weapons factory, developing deadly new bio-weapons for Radnor.
After Galen had created a particularly dangerous and mysterious toxin consisting of microscopic particles, an organic agent that was neither a virus nor a gas (but rather a substance absorbed by the body via lung-ingestion or perhaps through the skin), Dol Heep, an ambassador from the neighboring world of Avon, demanded that his world have exclusive rights to it, offering large sums of money to Galen to secure it.
Galen seemed eager to sell it to the Avoni and collect payment. However, due to the Radnoran's longstanding distrust for the Avoni, Curi convinced him to refuse the offer. Galen was upset and soon he was contacted by a furious Dol Heep. After promising him riches beyond anything he could dream of, Dol Heep had Galen unleash the toxin on his homeworld. The toxic particles, carried abroad on air currents and possibly spread from one being to another, proved to be so microscopic that not even a bacta bath would clear them all away. After killing millions of citizens in the city of Aubendo, the toxic cloud was soon poised, awaiting only a change in the prevailing winds, to make its way for the city of Tacto.
After many of Radnor's government officials fled the planet in panic, Galen assumed control of the evacuation and was coordinator of the rescue effort. When a team of Jedi led by Obi-Wan Kenobi, Soara Antana, Ry-Gaul, and Siri Tachi (together with their apprentices) arrived on Radnor to help with the evacuation process (and to curb rioting, looting, and general chaos), Galen quickly sent the Jedi Masters to the Isolation Sector, where they couldn't return because of the risk of inadvertently bringing the toxin back to the Clear Sector. Underestimating the Padawans, however, Galen's criminal activities were uncovered, and he was proven guilty of allying with the Avoni—helping them in their brazen, shameless takeover of Radnor after all of its citizens had died or fled the planet.
By the end of the crisis, Galen had been taken into custody by the Jedi. His sister, Curi, was enraged at the crimes he had committed and was perfectly willing to let him rot in prison. Amazingly, Dol Heep and the Avoni escaped justice, simply because of a general widespread desire to avoid the laborious, ongoing Senatorial debates that would inevitably erupt, only to drag on interminably over the matter.
- The Complete Star Wars Encyclopedia