For those who aren’t hip to such things, we’ve discussed the bowls in the past here, and you can view a gallery of them. For the most part, these appear in the Middle East about 500-600 AD (that number might be off, as I’m working from memory here). These bowls typically include a spiral pattern of writing inside, usually an incantation against demons, and are buried beneath the corners of buildings. Some say they are there to ward off demons, while others think their purpose is to trap them.
Most of these are clay, so the few that are actually made out of a human skull are especially notable. The article makes much of the fact that using them violates Judaic law regarding the handling of corpses. I’m not so sure I see that as crucial; there might have been ways around that, including having a person without religious qualms create these objects. At any rate, the same taboo that sets these remains apart might also be seen as granting them ideological power, thus making them prime candidates for this treatment.