Oh I love Temple style trashing, one of my faves.
Maybe this ruins your vision for the card, but if this were mine I'd move the "start of next turn" above the line, so it can just play the card normally when gained/trashed/discarded rather than behave differently; and then it would be an Action - Reaction - Duration, haha.
Monk $4 Action - Reaction
+2 Cards
Trash a card from your hand.
-
When you gain, trash, or discard this other than in Clean-up, you may play it.
Having it just be Trail with trashing didn't have a different enough feel for me to justify it being a new card. So now it's more like Masquerade with the Trail reaction, lol. Would be cool to chain Monks trashing each other for some draw.
Stepping Stone $3 Action - Reaction
+1 Card
+1 Action
-
When you gain or trash an Action or Treasure, you may trash this from your hand to play that card.
What about a card that Trail-ifies
other cards? And if you had multiple Stepping Stones in hand when you gain an Action or Treasure, you can play them all for free in addition to playing the gained/trashed card, and still only lose one. Pretty fun