The Spider Slayers known as the Delta-Nine Synthezoids are highly-enhanced synthezoids created by Doctor Octopus. Each member was synthesized from the DNA of Spider-Man, whom the Spider-Slayers were also designed to eliminate.
The Spider Slayers were a part of HYDRA scientist Arnim Zola's "Weapon S" program as clones engineered from Spider-Man, giving them all of his abilities plus their own, for the purpose of eliminating Spider-Man. While Doctor Octopus created them, Zola was the one who could control them. However, Doctor Octopus created Scarlet Spider so that he could lead and unite the Spider-Slayers as their commander. Unfortunately for Scarlet Spider, and unaware to Ock, Ock's unstable experiment, which he thought to be failure, Kaine has more absolute powers on commanding the Slayers than Scarlet.
It was revealed that the Scarlet Spider was merely an advanced Synthezoid version spliced with Spider-Man's DNA (similar to the Clone Saga) and the memories he had was implanted, and that he was originally meant to be the Delta-Nine Synthezoids' leader. As the two heroes struggle against the Synthezoids, Doctor Octopus (with improved Nano-tech) comes to the Spiders' aid and imprison the Synthezoids. After Zola gets reactivated, Doctor Octopuis betrayed Spider-Man and Scarlet Spider and left the heroes to the clones' wrath. Zola reactivates HYDRA Island's nanotechnology and traps Scarlet Spider and Spider-Man. Scarlet Spider feigns falling into his dark side and convinces the Spider-Slayers to not attack Spider-Man as the Web Warriors arrived. With help from the newfound allies, Spider-Man was able to defeat Zola. Escaping the HYDRA Island's destruction and placing the Delta-Nine Synthezoids into stasis pods, the Web Warriors and the Delta Nine Synthezoids go off to the Triskelion.
- In Marvel Comics, the Spider Slayers were robots created by Spencer Smythe to capture or destroy Spider-Man. In the Infinite Comics, the robot version of the Spider Slayers appear in it.
- Main article: Spider Slayers/Gallery