Doctor Odd’s Advent Calendar

Doctor Odd loved the holidays.
Every year, he’d craft some bizarre advent calendar, slowly revealing some nefarious plot to take over the world.
Or destroy it. Either way, he wasn’t picky.
This year’s effort would be his masterpiece.
Each day, he revealed a cure to some disease or affliction.
Cancer. AIDS. The common cold.
By the 24th day, he’d cured everything.
The world sang his praises on Christmas Day.
Then, Odd revealed his Nightmare Plague.
Why did he go through the trouble of creating all those cures?
He wanted a clean slate upon which to test his own newly-crafted disease.