Silver Hoard, Tumulus Trap Trigger
Within a dusty tumulus there can be found various items that the deceased owned in life. The items are all arranged neatly along the walls of the low ceilinged chamber and at the end is a panel carved in low relief depicting a hunting scene, a ritual involving a giant tree, and some sort of civic looking ceremony (perhaps an induction to public office). Without difficulty a player will notice that the panel is covering a niche which houses the silver hoard containing a number of silver rings, bars, armbands and coins. A careful player will notice that there are a number of coins laid in a geometrical shape to the fore. Detect-magic will show glowing lines connecting the coins in the front. If their arrangement is disturbed the spirit of the deceased will be roused (use poltergeist stats from the 5e monster manual). The primary attack of the poltergeist will be to throw things so be sure to have already described lots of heavy grave furnishings.