And so the Goddess said:

"As punishment for your crimes Kyubey, you are resigned to a fate forever purifying grief cubes. Using a hamster wheel that will represent Homura's many loops she went through to save me from your grasp as well as your current shackle to my law of cycles."

Hum. Is the third panel a reference to something? I recall this weird story where the immortals were in the habit of locking and retrieving memories by sticking the hand in the head and fondling the brain for a bit.

Edit: Hahaha, I just remembered what I was talking about. Acerolaorion and Araragi both do it in Nisemonogatari.