Miller's Grindstone

Once per Turn Action -

: Attack

When this hits a hero, clash with them. If you win, destroy the top card of their deck. If they win, put a -1

counter on this.

When a card is destroyed, it is put into the graveyard.
If the destroyed card has a triggered ability that says “When this is destroyed […]” it will not trigger because the triggered ability is not functional when the card is on the top of the deck.
You can still attack with Miller’s Grindstone even if it has 0.
If Miller’s Grindstone has 5 or more -1 counters on it, it’s power is still 0. Its is never negative.
Miller’s Grindstone only hits when it deals damage during the damage step of combat. If it attacks for 0 and there are no defending cards or prevention effects, it will not deal any damage and thus it will not hit.

Clash - Clashing heroes reveal the top card of their deck. The hero that reveals the card with greatest {p} wins.

Clash is an effect keyword.
Effects that modify values of cards in your deck are considered when clashing (e.g. Kayo, Mutated Mass, etc.)
If you win a clash, the opponent is considered to have failed to win the clash.
If no one wins a clash, you’re both considered to have failed to win the clash.
If both you and the opponent reveal a card with the same , no one wins the clash.
If both you and the opponent reveal a card without and/or don’t reveal any card, no one wins the clash.
If you reveal a card with and the opponent reveals a card without , you win the clash.
If you reveal a card with and the opponent doesn’t reveal any card, you win the clash.