Mogg Conscripts can't attack unless you've cast a creature spell this turn.
Legalities
Not Legal
Alchemy
Brawl
Explorer
Future
Gladiator
Historic
Modern
Oldschool
Penny
Pioneer
Standard
Standardbrawl
Timeless
Legal
Commander
Duel
Legacy
Oathbreaker
Pauper
Paupercommander
Predh
Premodern
Vintage
Rulings
2008-04-01
A “creature spell” is any spell with the type Creature, even if it has other types such as Artifact or Enchantment. Older cards of type Summon are also Creature spells.