Halcyon was born with strong magic. He dreamed of getting a government job where he could use his magic to help people. He studied and worked (writing a Bachelor's thesis on magical teleportation on the way), joined the army, and got recruited to the MSS.
He got stationed at the Bauhinian Embassy in Moreland as the cultural attache, during which he found a mistress and had a daughter.
After about ten years in Moreland, he was recalled to Bauhinia. He returned to find a country completely different from the one he left from. A normal person couldn't have felt anything off -- because they were not magicians.
At the airport, even before he crossed the customs, some MSS officers -- new, younger, he didn't recognize -- received him and immediately took him to a little office. They administered a level test, wrote down a number (which Halcyon didn't see), and told him to store his magic in a card nearly identical to his ID card. He did as he was told, and his magic was taken away from him.
He didn't understand what was going on. In Moreland, he had to keep his magic a secret in order to not attract the Moose too much; but this was a different story.
His magic was stripped from him. His teleportation paper (and nearly any other publication involving magic) was nowhere to be found. He lost contact of the magician club he belonged to. It was like magicians never existed.
That was when Moose spies reach out and said, "hey, your mistress and daughter miss you a lot."
From then on, Halcyon had been a mole in the MSS, spying for Moreland.
He got an apprentice, Pumpkin, who was a total pushover -- and he chose him for this exact reason. He cultivated Pumpkin into his agent, demanding absolute loyalty, and having him do dangerous tasks for Halcyon. The arrangement worked perfectly -- that is, until Pumpkin snapped.
It had to be done. It was the final stage of agent running, termination. Halcyon strangled Pumpkin in an alleyway and dumped the corpse in a landfill. Nobody would find out; he could go on spying. But the annoying kids got to him. (from A Nuke from Moreland)
He was captured and repeatedly tortured by his scary former subordinate to reveal the extent of his treachery. It was hard because he didn't even remember all of it.
He could've been sentenced to death, but the MSS traded him to Moreland instead. He was finally free and reunited with his mistress and daughter.