Originally posted by Eli shiffrin:
The core of the change is that we're no longer assuming split cards have two sets of characteristics when they're not on the stack. Some characteristics have multiple pieces of information very naturally—Destined to Lead is an instant sorcery, the same as Ornithopter is an artifact creature. It's black and green just like Winding Constrictor because its mana cost has B and G in it. Continuing that, the mana cost combines the components, and a card asking for Destined to Lead's mana cost sees 4BG
Edited Jean-François DURMONT (April 14, 2017 06:46:57 AM)
702.1b An effect that grants an object a keyword ability may define a variable in that ability based on characteristics of that object or other information about the game state. For these abilities, the value of that variable is constantly reevaluated.
Example: Volcano Hellion has the ability “Volcano Hellion has echo {X}, where X is your life total.” If your life total is 10 when Volcano Hellion’s echo ability triggers but 5 when it resolves, the echo cost to pay is {5}.
Example: Fire//Ice is a split card whose halves have the associated mana costs {1}{R} and {1}{U}. Past in Flames reads “Each instant and sorcery card in your graveyard gains flashback until end of turn. The flashback cost is equal to its mana cost.” Fire//Ice has “Flashback {2}{U}{R}” while it is in your graveyard, but if you choose to cast Fire, the resulting spell has “Flashback {1}{R}.”