Caseus Belli
Judging from the old records, Caseus Belli was not particularly dangerous. Name aside, it was simply a hard cheese made using a particular strand of bacteria; people who ate the cheese were slightly stronger, more vigorous, and could function for a full day at full capacity before exhaustion. Making it was finicky, which is why the only people who could do so were the Arval Brethren (a priestly college of the Roman Empire). When the Arval Brethren disappeared from history, so did Caseus Belli.