Sectumsempra, similar to Defodio, causes the target to fall over and slowly lose health. It takes approximately 15 seconds for them to die, in contrast with Defodio's 8 seconds. A blood decal will be placed under the target's body, which will grow over time.
Rennervate and Vulnera Sanentur/Episkey must be used in tandem with each other to counter the effects of Secumsempra; Rennervate will cause the victim to be unstunned, and Vulnera Sanentur will help the victim regenerate their lost health. If Rennervate is used, but Vulnera Sanentur/Episkey isn't, then the victim will still die.