Power Without Equal — ruling 1

The number of lands you control is checked as this scheme's triggered ability resolves. You can't play a land during your turn before it resolves.

Power Without Equal — ruling 2

If you control six or more lands, you'll draw three cards and get to cast three spells for free. No player may take any actions between the time you draw three cards and the time you finish casting free spells.

Power Without Equal — ruling 3

If you cast a card "without paying its mana cost," you can't choose to cast it for any alternative costs, such as emerge costs. You can, however, pay additional costs. If the card has any mandatory additional costs, such as that of Tormenting Voice, you must pay those to cast the card.

Power Without Equal — ruling 4

If the card has {X} in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.

Power Without Equal — ruling 5

You must cast any of the three spells you wish to cast for free while this scheme's ability is resolving. You'll have to pay the mana cost of any spells cast later in the turn, even if you cast fewer than three as you resolved this ability. The spells will be added to the stack in the order that you cast them.

Power Without Equal : règles, fonctionnement et interactions (MTG)

Power Without Equal 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 you set this scheme in motion, draw three cards. You have no maximum hand size until your next turn. If you control six or more lands, you may cast up to three spells from your hand without paying their mana costs.

How it works : Power Without Equal

Original English text — Wizards of the Coast / Scryfall

#1June 13, 2017· Wizards of the Coast
The number of lands you control is checked as this scheme's triggered ability resolves. You can't play a land during your turn before it resolves.
No other card is named in this ruling.
#2June 13, 2017· Wizards of the Coast
If you control six or more lands, you'll draw three cards and get to cast three spells for free. No player may take any actions between the time you draw three cards and the time you finish casting free spells.
No other card is named in this ruling.
#3June 13, 2017· Wizards of the Coast
If you cast a card "without paying its mana cost," you can't choose to cast it for any alternative costs, such as emerge costs. You can, however, pay additional costs. If the card has any mandatory additional costs, such as that of Tormenting Voice, you must pay those to cast the card.
No other card is named in this ruling.
#4June 13, 2017· Wizards of the Coast
If the card has in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.
No other card is named in this ruling.
#5June 13, 2017· Wizards of the Coast
You must cast any of the three spells you wish to cast for free while this scheme's ability is resolving. You'll have to pay the mana cost of any spells cast later in the turn, even if you cast fewer than three as you resolved this ability. The spells will be added to the stack in the order that you cast them.
No other card is named in this ruling.