Glancing Blow reveal condition

[iNano78]

I should know this...

Glancing blow:

When this creature is attacked, you must reveal Glancing Blow at the beginning of the Roll Dice step. If you do, that attack rolls 3 less attack dice (minimum 1 die). Then, destroy Glancing Blow.

If the attack doesn't make it to the Roll Dice step (e.g. because it gets canceled by a defense or something), do I still have to reveal and ultimately destroy Glancing Blow? Or do I only reveal Glancing Blow if the attack makes it to the Roll Dice step?

In other words, should I interpret the first sentences of the card text to read:

"When attacked, you must reveal Glancing Blow. During the Roll Dice step, the attack rolls 3 less attack dice."

Or

"When attacked, if the attack makes it to the Roll Dice step, then you must reveal Glancing Blow. Then this attack rolls 3 less attack dice."

[Obsidian Soul]

It says reveal at the beginning of the roll dice step.  If the attack is canceled or avoided before rolling dice, the necessary condition is not met for mandatory reveal, so the card should not be revealed.

[Zuberi]

The requirement includes revealing it during the Roll Dice step. If that step doesn't occur, then the requirement hasn't occurred and you won't be forced to reveal.

It might be clearer if you skip ahead to after the comma. "You must reveal Glancing Blow at the beginning of the Roll Dice step." Well, that sounds crystal clear to me. If there's no Roll Dice step, then there's no reveal. The specification of "when this creature is attacked" may seem a bit unnecessary since there is no such thing as a Roll Dice step anyplace other than attacks, but I still think it helps. It tells us what action we should be looking out for. I might have moved it to the end of the sentence though: "You must reveal Glancing Blow at the beginning of the Roll Dice step, when this creature is attacked."

Either way, the result is the same. Yes, being attacked is part of the trigger, but so is processing the Roll Dice step. You can't fulfill the instructions without both happening.

[zot]

it was likely done to help clarify that the spell decriments an actual attack rather then reducing upkeep condition rolls such as five burns.

[Zuberi]

Exactly. Those don’t actually have a Roll Dice step, but it could still confuse people who aren’t super familiar with the rules. Afterall, you ARE tolling dice. So specifying the attack requirement is unnecessary but helpful.