Master Rune of Valaya says:"Action: Cancel all damage assigned during the battlefield phase this turn. "

If I use a Tactic card to deal damage to opponent(unit or capital) at battlefield phase, could he use Master Rune of Valaya to cancel this non-combat damage?

The only requirement is that the damage be dealt during the battlefield phase. It does not specify the source or type of damage being dealt. So RoV would stop ALL damage dealt during the bf phase.

But, if the source of damage comes from a forced effect...it can not be inturrupted or cancelled by card effects. **** those Dwarf Rangers.

Thanks for answer.

Another situation

If I play tactic card to deal damage at an action window of declare defenders, then my opponent use Master Rune of Valaya to respond.

Which will be true?

1. Only that tactic card's damage can be cancelled.

2.all damage assigned after Master Rune of Valaya during the battlefield phase this turn will be cancelled.(combat damage or non-combat damage at later action window or trigger.)

3.others

Doc9 said:

Master Rune of Valaya cancels all damage during the combat phase. The only thing it doesn't cancel is "uncancellable damage". Forced effects cannot be cancelled, but the damage they deal can be. ( FAQ-Forced effects always occur immediately whenever their trigger is met, and they cannot be cancelled or interrupted by other actions. ) This means the Forced effect itself cannot be canceled (i.e. High Elf's Disdain), but the damage it does can still be cancelled.

Something happening at "Action" speed is not fast enough to interrupt a forced effect or a damage dealing tactic, because there is no window between assigning and applying damage. Master Rune of Valaya, however, sets up a constant effect once it resolves. That effect lasts until the end of the combat phase.

For the 2nd question, if he plays Master Rune of Valaya in response to your action, Valaya resolves first, which means that your tactic will deal no damage, and all combat damage (and damage from subsequent tactics in the combat phase) will be cancelled.

Entropy42 said:

Understood, You just have to make sure MRoV has been played prior to a forced effect for MRoV to stop the damage from that forced effect. Otherwise, you could not play MRoV in response to said forced effect and stop the damage since the forced effect occurs immediately. Got it.

Doc9 said:

Exactly. It has to have been played, and resolved, before a forced occurs. If its still on the stack and the forced goes off somehow (say something sacrificed to pay a cost while Dwarf rangers are out), then MRoV is not going to help.

Thank you, Entropy42.

So can I use Master Rune of Valaya at the action window of apply damage to cancel all damage assigned during the battlefield phase?(regardless which damage type/source they are except "cannot be cancelled" )

You can use it in the action window between assign and apply, and it will stop all combat damage. If you use it after other damage has already been applied, it doesn't go back and cancel that damage.

Entropy42 said:

I think it's just a little misunderstanding between us. But I got your point, so I use my words to say that again to see if my understanding is right.

For Example:

If I use Master Rune of Valaya at the action window of Assign Damage, then it can cancel all combat damage and all damage be assigned after this action during the battlefield phase.

If I use Master Rune of Valaya at the action window of Apply Damage, then it can't cancel combat damage, and it only can cancel the damage after this action during the battlefield phase.(although it's the last step of battlefield phase).

If I use Master Rune of Valaya at the action window of declare defender, then it can cancel all damage(include combat and non-combat damage) after this action during the battlefield phase.

Yes...you got it. MRoV needs to be played prior to any damage being applied for it to work. Otherwise...the damage is already applied and it is too late to stop it.