Unnerving Assault — ruling 1

The spell checks on resolution to see if any mana of the stated colors was spent to pay its cost. If so, it doesn't matter how much mana of that color was spent.

Unnerving Assault — ruling 2

If the spell is copied, the copy will never have had mana of the stated color paid for it, no matter what colors were spent on the original spell.

Unnerving Assault — ruling 3

Unnerving Assault affects only creatures on the battlefield at the time it resolves. If a creature enters later that turn, it won't be affected.

Unnerving Assault — ruling 4

If a creature changes controllers later in the turn, that won't change how Unnerving Assault affected it.

Unnerving Assault — ruling 5

The spell cares about what mana was spent to pay its total cost, not just what mana was spent to pay the hybrid part of its cost.

Unnerving Assault : règles, fonctionnement et interactions (MTG)

Unnerving Assault 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

Creatures your opponents control get -1/-0 until end of turn if was spent to cast this spell, and creatures you control get +1/+0 until end of turn if was spent to cast this spell. (Do both if was spent.)

How it works : Unnerving Assault

Original English text — Wizards of the Coast / Scryfall

#1August 1, 2008· Wizards of the Coast
The spell checks on resolution to see if any mana of the stated colors was spent to pay its cost. If so, it doesn't matter how much mana of that color was spent.
No other card is named in this ruling.
#2August 1, 2008· Wizards of the Coast
If the spell is copied, the copy will never have had mana of the stated color paid for it, no matter what colors were spent on the original spell.
No other card is named in this ruling.
#3August 1, 2008· Wizards of the Coast
Unnerving Assault affects only creatures on the battlefield at the time it resolves. If a creature enters later that turn, it won't be affected.
No other card is named in this ruling.
#4August 1, 2008· Wizards of the Coast
If a creature changes controllers later in the turn, that won't change how Unnerving Assault affected it.
No other card is named in this ruling.
#5August 1, 2008· Wizards of the Coast
The spell cares about what mana was spent to pay its total cost, not just what mana was spent to pay the hybrid part of its cost.
No other card is named in this ruling.