While I'm fairly familiar with the basic Spider-Man mythos, I have no idea who Van Atter is. According to Wikipedia, Nels Van Adder was a former research assistant who volunteered to become a test subject for an Oscorp serum. And you know that never goes well. It transforms him into the villain known as the "Proto-Goblin":
It was revealed that soon after Norman had Stromm arrested for embezzlement, he had found only a portion of the notes detailing his partner's serum. Norman tests the incomplete version of the serum on an Oscorp employee named Nels Van Adder, driving Van Adder slowly insane and beginning his transformation into a red, demon-like being known as the "Proto-Goblin." Killing several people and blaming Norman for what has happened to him, Adder proceeds to harass and later attempts to kill him before being knocked out a window in Oscorp by Arthur and George Stacy and fleeing into the wild. In order to escape conviction for what he had done to Van Adder, Norman convinces the police that Van Adder had been experimenting on himself, and that he had secretly been trying to help him. Van Adder's current fate remains unrevealed.Rhys Ifans has also been previously cast as the film's other villain, The Lizard. You might recognize Irrfan Khan from such films as Slumdog Millionaire and The Namesake. He's a good actor, and I hope his talents are used well, even if it's likely he'll acting under a ton of red demon-like makeup.