The Null Terror, the Full Deck BoneTender, was an unusual existence.
Null Terrors were odd creatures feared by all and almost always placed in the top five spots on the Universal Purge Banner in the Null Verse. They usually possessed powers and intelligence that allowed them to cheat higher level existences, corrupting or manipulating them in treacherous ways.
They were something akin to calamitous phenomena, but with high enough keenness of mind to act autonomously.
One such Null Terror was responsible for corrupting the Canon Men, turning them from do-gooders who helped the Four Authorities maintain balance in the Null Verse to maniacs who opposed the very balance of Serenity's treasure.
The BoneTender had been far removed from such treachery, however.