804.1
The Emperor variant always uses the deploy creatures option, and it can be used in other variants that allow players to compete in teams. Multiplayer formats in which players compete as individuals usually don't use this option.
Historical Rules · Effective 1 May 2013
Read Section 804 continuously, or open any rule on its dedicated page.
Chapter 8 · Multiplayer Rules
Section 804
2 rules
The Emperor variant always uses the deploy creatures option, and it can be used in other variants that allow players to compete in teams. Multiplayer formats in which players compete as individuals usually don't use this option.
Each creature has the ability "{T}: Target teammate gains control of this creature. Activate this ability only any time you could cast a sorcery."