Errantry

Enchant Creature    (CMC:2)

Enchant creature Enchanted creature gets +3/+0 and can only attack alone.

"There is no shame in solitude. The lone knight may succeed where a hundred founder."

124 ME2 • ENScott Kirschner

™ & © 1993—2008 Wizards of the Coast

Legal in: Ice Age Block,Legacy,Vintage,Freeform,Prismatic,Tribal Wars Legacy,Singleton 100,Commander

Oracle Text (click to copy):

10/1/2008
"Can only attack alone" means the enchanted creature can't be declared as an attacker during the declare attackers step unless no other creatures are declared as attackers at that time (either by you or your Two-Headed Giant teammate).
10/1/2008
If the enchanted creature attacks alone, then a spell or ability causes another creature to be put onto the battlefield attacking, that's fine.