The Diadem
From Tardis Wiki, the free Doctor Who reference
The Diadem was a mind parasite that was implied to be related to the Keller Machine mind parasite. (NA: Legacy)
Description
The Diadem was first seen on Pakha that influenced the native inhabitants to becoming warlike, and thus they were at war constantly, the diadem did not not the entire race, as there were some pacifist who attempted to change their society for the better. (NA: Legacy)