Deragon, Rightful Heir

Deragon, Rightful Heir has indestructible as
long as your opponent has an untapped land.
{1}{w}: Target creature you don't control gets
-1/-1 until end of turn and can't have less than
1 toughness. You may tap your opponents lands
to pay for this ability. Activate during combat
only. (Only to pay for this ability and can't tap land
just to tap them. Opponent can't tap lands for mana
Deragon, Rightful Heir tapped.)