Until the end of your next turn, you may play it
Whenever another nontoken creature enters the battlefield under your control, you may pay
(2019-10-04) An effect may refer to a card, spell, or permanent that "has an Adventure." This refers to a card, spell, or permanent that has an adventurer card's set of alternative characteristics, even if they're not being used and even if that card was never cast as an Adventure
The first thing to consider is the way you want to build a deck
Now, all of a sudden, all the Clues you pile up aren't just future card advantage, but they're now also extra Artifacts that can be tapped, sacrificed, or otherwise turned into mana and value, which makes the whole engine feel a lot more explosive than it first appears
See this page for details on the contents of each theme