His gadgets, along with Beck’s hypnosis skills, can convince his victims that they’re seeing or experiencing things that aren’t actually happening.
Both Kraven the Hunter and Mysterio have been Spider-Man adversaries since the superhero’s early Silver Age years, with Mysterio debuting in The Amazing Spider-Man #13 and Kraven arriving two issues later.
He’s also created chemical weapons that have weakened Spider-Man’s abilities many times, including the hero’s trademark Spider-sense.