Season of the Witch — ruling 1

At the beginning of every end step, regardless of whose turn it is, the second ability triggers. When it resolves every creature that could have been declared as an attacker during that turn’s Declare Attackers Step but wasn’t will be destroyed.

Season of the Witch — ruling 2

A creature won’t be destroyed if it was unable to attack that turn, even if you had a way to enable it to attack. For example, a creature that had summoning sickness wouldn’t be destroyed even if you had a way to give it haste.

Season of the Witch : règles, fonctionnement et interactions (MTG)

Season of the Witch 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 your upkeep, sacrifice this enchantment unless you pay 2 life. At the beginning of the end step, destroy all untapped creatures that didn't attack this turn, except for creatures that couldn't attack.

How it works : Season of the Witch

Original English text — Wizards of the Coast / Scryfall

#1September 20, 2013· Wizards of the Coast
At the beginning of every end step, regardless of whose turn it is, the second ability triggers. When it resolves every creature that could have been declared as an attacker during that turn’s Declare Attackers Step but wasn’t will be destroyed.
No other card is named in this ruling.
#2September 20, 2013· Wizards of the Coast
A creature won’t be destroyed if it was unable to attack that turn, even if you had a way to enable it to attack. For example, a creature that had summoning sickness wouldn’t be destroyed even if you had a way to give it haste.
No other card is named in this ruling.