jonesy
A Wicked Kendragon
The mummy might as well be holding a sign saying 'the gem is a trap'.The sarcophagus contains a mummified human corpse partially wrapped in bandages. You can just barely see a huge amethyst under the wrappings that cover the corpse's head.
What do you think the chances are that someone might find the ring? It doesn't say whether the ring is clearly visible or under wrappings. And the description of Detect Magic in 1e is vague enough that it makes me wonder whether the gem might mess up the detection.