Solitary Hunter // One of the Pack

Creature — Human Warrior Werewolf

At the beginning of each upkeep, if no spells were cast last turn, transform Solitary Hunter.

3/4

Creature — Werewolf

At the beginning of each upkeep, if a player cast two or more spells last turn, transform One of the Pack.

5/6

2016-04-08:
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.
2016-04-08:
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.
2016-07-13:
For more information on double-faced cards, see the Shadows over Innistrad mechanics article (http://magic.wizards.com/en/articles/archive/feature/shadows-over-innistrad-mechanics).