Fall of the Titans

Fall of the Titan's mana value is based on its mana cost of {X}{X}{R}, even if you're casting it for its surge cost. For example, if you cast Fall of the Titans for its surge cost and choose 4 for X, its mana value will be 9.

Wotc — January 22, 2016

For some cards, surge represents only an alternative cost, a discount that applies if you or a teammate has cast another spell this turn. Other cards, like Reckless Bushwhacker, have additional abilities or effects if you paid the surge cost to cast the spell.

Wotc — January 22, 2016

The other spell that you or a teammate cast can be one that's resolved, one that was countered, or (for instants with surge) one that's still on the stack.

Wotc — January 22, 2016

If an instant or sorcery spell cast for its surge cost is copied, the copy is also considered to have had its surge cost paid.

Wotc — January 22, 2016

Casting a spell for its surge cost doesn't change its mana cost or its mana value.

Wotc — January 22, 2016