The gatekeepers primary tool of the trade. A seal by itself is useless until its infused with a fragment of a soul. The infused soul is refereed to as a subject because the owner of the seal can summon this fragment and sync it within their own soul. This allows the host to use the original souls powers albeit at a much less potent rate.
There are two main steps to complete in order to fashion a new seal. The first step is to obtain a fragment of a soul. The second is to craft a seal that is powerful enough to contain it. The first step can be accomplished through a ritual with the soon to be subject in which the Sealer links up their Will to the Sealees soul and absorbing a part of it. The second step is to take the seal, also called a card, and transferring the absorbed soul into it. If the soul is too powerful for the seal the ritual fails and they must restart.
To use a Seal you must take your will and infuse it into the card. The fragment inside the card then merges with your soul temporarily. The card/seal only has so much power before the fragmented soul dissipates and the card must recharge. When in use the subjects appearance and abilities merge with the user. It can be described as an apparition of the original subject that obeys whoever summoned it.
Some Subjects can only be properly summoned through a Ritual. Once completed, whatever it is, the Subject is summoned.