Rivets was the head of Stable 99's maintenance, a strong-headed mare, and instigator of the insurrection against the Overmare. Frequented card games in the stable's lower levels and regularly made class B violations in the form of cigar smoking. Blackjack never reported her on it and the manufacturing of them remained a mystery.
After Deus' attack on Stable 99, Rivets led a portion of the population into hiding in the maintenance levels while the Raider Disease infected those above. After Blackjack returned (in chapter 22) and put down those with the disease, Rivets and the other survivors were free to reoccupy the Stable, however they too succumbed to the engineered virus and Rivets was gassed along with the rest of the Stable by Blackjack and was the second-last pony to see her killer before Lacunæ rescue-teleported the Security Mare.