I don't know based on the rulebook. The provided context specifies on page 28 that "Whenever you defeat the Demons, you must trash a card. If you cannot trash a card from your hand or discard pile, you..." but the sentence is cut off and does not provide the full rule. There is no further information in the provided context about what to do if you have no cards in hand, discard, or play area when required to trash a card.

To answer this question definitively, the complete rule or additional context from the rulebook would be needed.

Source: Core Rulebook (pp. 13, 23, 28, 29)