Cold ghosts

The hardest part of fighting ghosts is you have to do it cool.

Ghosts eat heat, so any energy you pour into your weapons systems only makes them stronger. That’s why we need to capture them, of course, but it makes things damn hard. For the strong ones, just keeping your body temperature up is a challenge, and not one that the insulating sigils are always equipped to handle. That’s how ghost-hunters die. Not that NASA cares, of course.

Thinking some more about the world of this story and maybe this one?

Let’s say the afterlife is part of the universe. Let’s also say that ghosts are cold. How would ghost-assisted heat-dumping work then?

Perhaps ghosts are the 3D cross-sections of higher-dimensional objects, so they are no more violating the laws of thermodynamics than a heat sink sticking up from the surface of a flat circuit-board.

As for the machinery needed to keep the ghost in place: perhaps pentacles, ghost jars, etc. are the equivalent of bolts that attach the heat sink to the board (and maybe some spiritually conductive wires). Alternately, you could just persuade the ghost to hang out there.

And I’d say the best place to use this technology would be space.