Necrovalley and Royal Tribute

necrovalley on opponent's field. can i activat royal tribute, or i must hav necrovalley on my side of the field?

Tribute's effect states:

Activate only when you control "Necrovalley". Both players discard all Monster Cards in their hands to the Graveyard.

This means you must have a necrovalley of your own in order to activate it. If you don't have one you can't play it.

+1 what DJD say.Original text of the RT was:
"This card can only be activated when your "Necrovalley" is active on the field. Both players must discard all monster cards in their hand to the Graveyard."

but Konami change it to:
"This card can only be activated when "Necrovalley" is on your side of the field. Both players discard all Monster Cards in their hands to the Graveyard."

or
"Activate only when you control "Necrovalley". Both players discard all Monster Cards in their hands to the Graveyard."

So ya now Konami make change and you can't use RT when your opponent have Necrovalley.

Actually if you read the old text carefully it's still the same.

This card can only be activated when your "Necrovalley" is active on the field. Both players must discard all monster cards in their hand to the Graveyard.

The effect has never changed. They changed the text because a simpler text would be easier to understand.

uh ya :d <3