Great assignment. I'm really intrigued by the esoteric possibilities of "portals". I hope I'm not slightly askew of the specific "portal" theme by thinking of windows as well as doors but I have heard or read (???) that the camera lens is a window to the human experience and the eyes are windows to the soul. I have pondered the possibilities of a camera lens and eyes (eye) in a photo and made this photo.
I opened the back af a 1914 era Kodak autographic, aimed it at the eye of one of my wifes dolls. I then took a picture from its film side and through it's lens using a Kiev 60 with an 80mm lens and 75mm extension. I'm not sure what I expected but here's my photo of "portals".