Free matter is the state of matter that makes up a Risen being once their soul or spirit becomes freeactive.
The type of matter that free matter is is just that. Free. A Risen’s body that is now free matter cannot be repressed for any significant amount of time. But it can be destroyed. The time a Risen’s body can be repressed can vary from none to roughly 72 hours. It all depends on how good a Risen is at being freeactive.
The soul or spirit must remain freeactive in order for the Risen’s body to remain in its free matter state. Otherwise, the body can once again become oppressed.