Wizards of the Coast has revealed the mechanics for the upcoming Magic: The Gathering set Zendikar Rising during today's spoiler launch livestream at Twitch.tv/magic, and two of the mechanics are new: the modal double-faced cards and the party mechanic.
The party mechanic highlights four specific creature types: Cleric, Rogue, Warrior, and Wizard. According to Wizards, "The number of creatures in your party is how many of those roles you can fill with a creature you control. Each creature you control can fill a maximum of one role."
Check out these cards that use the party mechanic:
Zendikar Rising will feature a good amount of Clerics, Rogues, Warriors, and Wizards, and some creatures will be versatile like Tajuru Paragon, which can count as any of those creature types, but each copy of this card only fills one role in the party.
Zendikar Rising is all about adventure, and I think the party mechanic fits well with the set's themes.