Calum Snyder is the son of Len and Kase and is Kamen Rider Hydra Bat. He was always aware of his parents Kamen Rider work. He usually stayed around the Riders Headquarters being looked after by Eubulon or other off duty Riders. However, when he was seven years old he was captured by Xaviax and was held hostage for a week before Xaviax appeared outside the Riders Headquarters. He ordered for the Riders decks or Calum would be destroyed. Calum told the Riders to not give the decks over as he knew the danger of the outcome. When the Riders refused Xaviax infected Calum with a virus that drained his life energy. The Riders acted quickly to get Calum into the Headquarters and find a way to slow the process until the could find a cure for the virus but they couldn't stop it. Eubulon knew a way to stop it, the 12 Riders would have to project their Advent Deck's energy which would encase the virus inside a newly formed Kamen Rider Deck. The way the occurred was when Eubulon extracted the virus for a very short time and then took the Riders' energy and " warped " virus inside, he finally solidified the energy which created the Hyrda Bat Deck, a combination of all 12 Riders' energy and Xaviax's Virus, making it one of the strongest Decks out of the original 12. The only problem with this solution is that if Calum were unbinded for his Deck, the virus would escape and infect Calum.