The multiple-worlds theory of cosmology allows room for every religion's Heaven and Hell and other planes to coexist, with the similar planes of all the sapient beings of all the worlds in all the galaxies...How often do the wires get crossed, as it were, leaving your paladin in a Hell for hedonistic lizards, for example.
Purple deer have begun to appear near the ruins of a fallen city, or other place of power. Hunting the deer is absurdly easy, as their coloration makes them easy to see. The heros prepare a feast from a freshly killed deer find out several hours later that the meat of the new purple deer is poisonous. This can range from cramps and vomiting to the truly sinister and lethal.