Galen clenched his fist. Orson Krennic, the man he once called his friend. He realized too late that this man was never a friend. Krennic had used him for his own plans. He was still using him like a tool. When the truth came to Galen, he managed to escape and hide with his family on Lah’mu. Until the day Krennic found them.

Now he was a hero of the Empire, which meant nothing more than being a prisoner.
They used his research to develop a superweapon, a weapon that could destroy entire planets. They called it the Death Star, a name that really fitted. How many deaths had he already caused? Not just his wife, there were many more. Scientists who had disappeared or fallen victim to an accident when they refused to stay in the weapons research program.
He had to end it once and for all.

Galen had built a flaw into the weapon. A flaw that only he knew existed. A hit near this flaw would cause the entire battle station to explode.

He had wondered how he could inform the Alliance about this flaw. And one day a plan came to him.
He had befriended a young Imperial freighter pilot named Bodhi Rook. The young man came from Jedha, a moon where the Empire was plundering the kyber crystals of the ancient Jedi temple. Galen learned from Bodhi that Saw Gerrera, an old friend of the Erso family, had founded a rebel cell there. Perhaps Jyn was still with him, and perhaps Saw could deliver his message to the Alliance.

That day, he had asked Bodhi to be his messenger. He had told him that he could make things right if he was brave enough. Galen was well aware that it was treason to ask an Imperial pilot to desert and make contact with the so called rebels.
But he owed the Empire nothing. He wanted the Empire to pay for what it had done to him and his family. Galen Erso wanted revenge.
Determined, he rose from his seat and went into the hologram chamber. There he activated the device and began recording. He knew that this was the only way to pay for his sins and get revenge.