A forbidden item, the Hazard Trigger was given to Sento by Blood Stalk. The only way to stop the rampaging Ryuga is to harness the power of the Hazard Trigger. However, the Hazard Trigger was classified as a “forbidden item” due to its side effects. It is a weapon of destruction that causes the user to lose sight of himself and rampage after a certain time limit has expired… (Source: kamenrider.fandom)