Trinisphere | Magic: The Gathering
Formats Trinisphere is Legal in
Official Oracle Text for Trinisphere
Official Rulings for Trinisphere
12/1/2004 : Even with a cost reducer on the battlefield, spells can't cost less than three mana to cast.
12/1/2004 : If a spell costs at least three mana due to additional costs, such as kicker costs, that's fine.
12/1/2004 : You still need to pay any additional nonmana costs the spell has, such as sacrificing a creature or discarding cards.
12/1/2004 : Casting a creature with morph face down already costs three mana, even though the converted mana cost of the face-down spell is zero, so Trinisphere normally doesn't modify the total cost of a face-down creature spell. However, if Dream Chisel is reducing that cost while Trinisphere is on the battlefield, you'll still have to pay three mana for the spell.