Board Thread:Ask Questions/@comment-32811824-20171003074711/@comment-31953669-20171003111201

Taken directly from the Pestilence page So if Pestilence weren't unique, it could win with other pestilences
 * If an Amnesiac remembers that they were Pestilence, Horseman of the Apocalypse, becomes Pestilence , and wins, both Pestilence  will win.