Thank you all for your thoughtful discourse, let’s wrap this one up! This scenario appears at first to be a perfect fit for the newest change to trigger policy, which says that if a trigger causes a visible change to the board or requires a choice on resolution, that action or choice must be made before changing steps or casting something at sorcery speed, in order for the trigger not to have been missed. However, there’s a very important detail to note about the bolster trigger: As it resolves, it requires a choice between creatures you control with the least toughness.

By indicating her choice of Champion of Arashin before attacking, Anna satisfied the conditions for acknowledging the trigger. However, she unfortunately did not finish resolving the trigger by placing the counter on to her creature. As such, she committed a Game Rule Violation and will receive a warning. Nalick, by not preventing this error, also has some responsibility for the error and as such receives a warning for Failure to Maintain the Game State. As relatively little time has passed since the error, and no partial fixes are applicable to this situation, we will rewind the situation to the point of the mistake. Anna’s attacking creatures will be untapped, and the game resumes during her main phase when the bolster trigger is resolving.