Skullcage — ruling 1

Skullcage’s ability deals damage if the player has zero, one, two, five, or more than five cards in hand when its ability resolves.

Skullcage — ruling 2

Skullcage doesn’t check hand size when it triggers, only when it resolves.

Skullcage : règles, fonctionnement et interactions (MTG)

Skullcage 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 opponent's upkeep, this artifact deals 2 damage to that player unless they have exactly three or exactly four cards in hand.

How it works : Skullcage

Original English text — Wizards of the Coast / Scryfall

#1December 1, 2004· Wizards of the Coast
Skullcage’s ability deals damage if the player has zero, one, two, five, or more than five cards in hand when its ability resolves.
No other card is named in this ruling.
#2December 1, 2004· Wizards of the Coast
Skullcage doesn’t check hand size when it triggers, only when it resolves.
No other card is named in this ruling.