Clocknapper — ruling 1

To steal a phase means that during that player’s next turn, as the chosen phase begins, you treat it as if it were your turn. Here’s what happens if you steal each phase:

Clocknapper — ruling 2

Beginning phase: You untap permanents you control and your opponent doesn’t. Abilities that trigger at the beginning of your upkeep happen and ones that trigger at the beginning of their upkeep don’t. You draw a card as it’s now your draw step, so your opponent doesn’t.

Clocknapper — ruling 3

Precombat main phase: You can cast all types of spells while your opponent can only cast instants and spells with flash.

Clocknapper — ruling 4

Combat phase: Just like combat on your turn, you can attack your opponents with your creatures. The opponent you stole the phase from can’t attack with their creatures, but they can block.

Clocknapper — ruling 5

Postcombat main phase: Same as precombat main phase.

Clocknapper — ruling 6

Ending phase: Most abilities that trigger during the end step don’t care whose turn it is, but a few do. Effects that last “until end of turn” or “this turn” will expire as normal, as they also don’t care whose turn it is.

Clocknapper : règles, fonctionnement et interactions (MTG)

Clocknapper 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

When this creature enters, choose beginning phase, first main phase, combat phase, postcombat main phase, or ending phase. Steal that phase from target player during their next turn. (That phase occurs as though it's your turn instead.)

How it works : Clocknapper

Original English text — Wizards of the Coast / Scryfall

#1January 19, 2018· Wizards of the Coast
To steal a phase means that during that player’s next turn, as the chosen phase begins, you treat it as if it were your turn. Here’s what happens if you steal each phase:
No other card is named in this ruling.
#2January 19, 2018· Wizards of the Coast
Beginning phase: You untap permanents you control and your opponent doesn’t. Abilities that trigger at the beginning of your upkeep happen and ones that trigger at the beginning of their upkeep don’t. You draw a card as it’s now your draw step, so your opponent doesn’t.
No other card is named in this ruling.
#3January 19, 2018· Wizards of the Coast
Precombat main phase: You can cast all types of spells while your opponent can only cast instants and spells with flash.
No other card is named in this ruling.
#4January 19, 2018· Wizards of the Coast
Combat phase: Just like combat on your turn, you can attack your opponents with your creatures. The opponent you stole the phase from can’t attack with their creatures, but they can block.
No other card is named in this ruling.
#5January 19, 2018· Wizards of the Coast
Postcombat main phase: Same as precombat main phase.
No other card is named in this ruling.
#6January 19, 2018· Wizards of the Coast
Ending phase: Most abilities that trigger during the end step don’t care whose turn it is, but a few do. Effects that last “until end of turn” or “this turn” will expire as normal, as they also don’t care whose turn it is.
No other card is named in this ruling.