To trigger the Werewolf's back face's transform ability, a single player must have cast two or more spells during the previous turn. If multiple players each cast just one spell during the previous turn, the ability won't trigger.
2016-04-08
wotc
The abilities that transform a Werewolf back and forth look at the entire previous turn, even if the Werewolf with that ability wasn't on the battlefield for some or all of that turn.
Format Legality
Standard
Not Legal
Future
Not Legal
Historic
Legal
Timeless
Legal
Gladiator
Legal
Pioneer
Legal
Modern
Legal
Legacy
Legal
Pauper
Legal
Vintage
Legal
Penny
Not Legal
Commander
Legal
Oathbreaker
Legal
Standardbrawl
Not Legal
Brawl
Legal
Alchemy
Not Legal
Paupercommander
Legal
Duel
Legal
Oldschool
Not Legal
Premodern
Not Legal
Predh
Not Legal
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