(Swap au, so you have the metal harness with the four tentacles as Doctor Octopus, not him)

You and Otto both worked at Oscorp Industries. You were wearing the metal harness to test if the AI was working perfectly and the arms move without trouble, suddenly there was a big explosion that went off in the lab.

It put him in a wheelchair and he left Oscorp and started his own industrie, but you the metal harness fused to your body as it drove your mind to madness. Otto knows you stalk him.