The Big Idea — ruling 1

If you use the second ability to roll two dice instead of one, any ability that triggers “whenever you roll a die” will trigger twice.

The Big Idea — ruling 2

If another spell or ability instructs you to roll two dice and use the difference, you can use The Big Idea’s second ability to replace one of those die rolls. First, roll two dice and use their sum. That’s the first result. Then roll one die. That’s the second result. Then figure out the difference between those two results.

The Big Idea — ruling 3

Some cards, like Chittering Doom, care about the results of individual die rolls and not the total if two dice are rolled together. For example, if you use The Big Idea’s second ability to replace one die roll with two and roll two 3s, Chittering Doom’s ability (which triggers whenever you roll 4 or higher on a die) won’t trigger.

The Big Idea : règles, fonctionnement et interactions (MTG)

The Big Idea 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

, : Roll a six-sided die. Create a number of 1/1 red Brainiac creature tokens equal to the result. Tap three untapped Brainiacs you control: The next time you would roll a six-sided die, instead roll two six-sided dice and use the total of those results.

How it works : The Big Idea

Original English text — Wizards of the Coast / Scryfall

#1January 19, 2018· Wizards of the Coast
If you use the second ability to roll two dice instead of one, any ability that triggers “whenever you roll a die” will trigger twice.
No other card is named in this ruling.
#2January 19, 2018· Wizards of the Coast
If another spell or ability instructs you to roll two dice and use the difference, you can use The Big Idea’s second ability to replace one of those die rolls. First, roll two dice and use their sum. That’s the first result. Then roll one die. That’s the second result. Then figure out the difference between those two results.
No other card is named in this ruling.
#3January 19, 2018· Wizards of the Coast
Some cards, like Chittering Doom, care about the results of individual die rolls and not the total if two dice are rolled together. For example, if you use The Big Idea’s second ability to replace one die roll with two and roll two 3s, Chittering Doom’s ability (which triggers whenever you roll 4 or higher on a die) won’t trigger.
No other card is named in this ruling.