Mistress Tess likes Her slaves to be functional, to serve a purpose, whether that be to suffer or serve. On this occasion Her slave is needed to serve, but as his servitude is only to be Her ashtray She doesn't need any part of his body other than his head, or more specifically his mouth. Trapped in stocks the slave has nothing to do but keep its mouth open awaiting the gift of ash from his Goddess.

Mistress Tess likes Her slaves to be functional, to serve a purpose, whether that be to suffer or serve. On this occasion Her slave is needed to serve, but as his servitude is only to be Her ashtray She doesn't need any part of his body other than his head, or more specifically his mouth. Trapped in stocks the slave has nothing to do but keep its mouth open awaiting the gift of ash from his Goddess.