A huge moon, with a three-coned volcano which can be seen from the planet when it erupts and is taken for an omen. The planet, smaller than the moon, orbits it, and the planet in turn is orbited by a very small but very hot and bright ball of flame.
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.