Phantom image core was a floating mechanical boss of the second base of Contra. It is capable of making "phantom" duplicates of itself. The image core is vulnerable to attack when the phantom images come back together. It attacks with projectiles that can be shot down but follow the player in a looping arc.
In Contra 4 this boss reappears as the boss of the 3rd level (Base). In here he periodically splits into 2 virtual blinking images that initially separate a short distance before retracting and merging. They merge at a different spot each time. All heads, whether merged or virtual, emit Bubble Dimers. After receiving some damage, they take longer to merge, moving around and crossing over each other a few times before doing so. In this first phase, the boss is vulnerable only in the single, merged form. At the beginning of the battle, 4 Barrels are dispensed from 4 holes at the base of the wall. Afterwards, only 2 are dispensed at a time, from holes that are selected randomly. Throughout the first phase, Base Security Soldiers periodically appear. After receiving enough damage, phase 2 begins. Here, the boss stops forming virtual images. Instead, the intact head rapidly and eccentrically moves left and right. It emits Bubble Dimers more frequently. All other enemies and objects stop appearing. The boss is now permanently vulnerable.