How does Treasure Trove work? Can it only be used once, why does it need to be tapped, and does it require recycling a purple rune?

Ruling: Treasure Trove can only be activated once because after you kill it, it goes to your trash and cannot be activated again. You must exhaust it as part of its cost and pay one purple rune to activate it.

Nuances:

• In competitive play, it is most commonly combined with Pack of Wonders to get consistent value
• Can be used in combo with Heimerdinger