Tomeltai

A red card is a card with a red color bar (usually at the top of the card).

“When this attacks” is a triggered effect that triggers when the dragon is considered to have attacked, during the attack step. It does not trigger if the combat chain closes in the layer step of combat. After it triggers, it will still resolve even if the dragon ceases to exist or the combat chain closes.

If you only have 1 card your deck you reveal that card.

Revealing cards is not optional, even if the hero does not control any equipment.

If you do not reveal 1 or more red cards this way, do you do not put a -1 counter an equipment and you do not destroy an equipment with 0.

The cards are revealed before the equipment is selected and a -1 counter is put on it.

You can put a -1 counter on an equipment that does not have a defense property, but it will not be destroyed because it does not have 0.