Underneath Eggeater's Shrine is a direct connection to the primordial earth- and its spoils. This is Eggeater's treasure room, dug up from the deepest parts of the world where no surface-dweller has ever trod.
The chamber has shallow earthen walls and was clearly dug by the great snake itself- it cared little for its appearances. There is a divot in the center of the chamber where the snake could once have dug to the center of the world to bring back its spoils. Now, the earth has closed back around it. You can see sparkling things in the snady pit- gemstones left behind from its previous trips below. Each turn you dig, you found gemstones of every color and type, mostly fancy and semi-precious with a few truly rare ones there too, varying in size from as large a a baby's fist to jewels that fill your pocket like an apple.
The first turn you dig, you find 10,000 gp worth of gems. Every turn after, you find 1000 less. If Eggeater still lives, you have a 1 in 6 chance of him returning and attacking you for trespassing in his lair.