"There is no shame in solitude. The lone knight may succeed where a hundred founder."
—Arna Kennerüd, skyknight

Masters Edition II

Errantry

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

Enchanted creature gets +3/+0 and cannot attack during any turn in which any other creatures attack.

"There is no shame in solitude. The lone Knight may succeed where a hundred founder."
—Arna Kennerüd, Skyknight

Target creature gets +3/+0. If that creature attacks, no other creatures can attack this turn.