The Emperor’s Plague was a mutagenic plague developed by Evir Derricote that only killed Humans. It was more deadly than the Krytos virus which killed millions of aliens on the planet Coruscant following the New Republic capture of Coruscant in 6 ABY. It was said to be so horrible that even Emperor Palpatine feared to deploy it.
This plague was stored at an uncharted asteroid known as the Emperor’s plague storehouse. In 24 ABY, a sample of it was obtained by an information broker, Fonterrat, who sold it to Nolaa Tarkona. During the Battle of the Emperor’s Plague Storehouse, a team of Jedi, with Bornan Thul, destroyed all canisters containing the disease along with other alien-specific plagues, stopping the Diversity Alliance‘s genocidal anti-human crusade.