I’ve encountered a bug of the vanar trial progress reset after completed, submitting to the support and they replies that Oak in the nemeton can only be played when you have at least 5 tokens on the battle field, so even if you completed the trial at last turn, you still not allow to play it if your opponent clears your board. It obviously contradicted with the trial mechanism “Once a Trial is complete, the card remains unlocked for the duration of the game, even if the condition is no longer met.”
Plz play the game, support team.