|< ID Card 83||All ID Cards||ID Card 85 >|
ID Card #84 is a collectible item in Dead Island, and can be found in the Laboratory map of Act III. It is part of the My collectibles, let me show you them! challenge, and the Gotta find'em all and Nearly there achievements.
When you walk out of the lab, in front of the green car, theres a dead body, next to that body is the ID.
Can be seen on the following map: