Breakneck Rider // Neck Breaker — ruling 1

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.

Breakneck Rider // Neck Breaker — ruling 2

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.

Breakneck Rider // Neck Breaker : règles, fonctionnement et interactions (MTG)

Breakneck Rider // Neck Breaker is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

At the beginning of each upkeep, if no spells were cast last turn, transform this creature. Attacking creatures you control get +1/+0 and have trample. At the beginning of each upkeep, if a player cast two or more spells last turn, transform this creature.

How it works : Breakneck Rider // Neck Breaker

Original English text — Wizards of the Coast / Scryfall

#1April 8, 2016· Wizards of the Coast
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.
No other card is named in this ruling.
#2April 8, 2016· Wizards of the Coast
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.
No other card is named in this ruling.