Errantry

{1}{R} · Enchantment — Aura

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

Motor: se resuelve a mano

Rulings (2)

“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).
Wizards of the Coast · 2008-10-01
If the enchanted creature attacks alone, then a spell or ability causes another creature to be put onto the battlefield attacking, that’s fine.
Wizards of the Coast · 2008-10-01