Oracle

Instant - Trap 

If an opponent had two or more lands enter the battlefield under their control this turn, you may pay 3RR rather than pay this spell's mana cost.
Destroy two target lands. Lavaball Trap deals 4 damage to each creature.

Tournooi-info

Legal in: Vintage, Legacy, Modern, Commander

Officiele rulings

10/1/2009
You may ignore a Trap’s alternative cost condition and simply cast it for its normal mana cost. This is true even if its alternative cost condition has been met.

10/1/2009
Casting a Trap by paying its alternative cost doesn’t change its mana cost or converted mana cost. The only difference is the cost you actually pay.

10/1/2009
Effects that increase or reduce the cost to cast a Trap will apply to whichever cost you chose to pay.

10/1/2009
You may target any two lands, not just ones that entered the battlefield this turn.

10/1/2009
All creatures are dealt damage, not just ones controlled by the targeted lands’ controller(s).

10/1/2009
If both targeted lands are illegal targets by the time Lavaball Trap resolves, the entire spell doesn’t resolve. No creatures are dealt damage.

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