Subtlety — ruling 1

Subtlety's triggered ability targets a spell on the stack. It can't target creatures or planeswalkers on the battlefield.

Subtlety — ruling 2

A spell that's put into its owner's library doesn't resolve, but it isn't countered. This will work on spells that say they can't be countered.

Subtlety — ruling 3

The owner of the spell is the one who chooses whether it goes on the top or bottom of their library. All players will know this information.

Subtlety — ruling 4

To determine the total cost of a spell, start with the mana cost or alternative cost you're paying (such as an evoke cost), add any cost increases, then apply any cost reductions. The mana value of the spell is determined by only its mana cost, no matter what the total cost to cast that spell was.

Subtlety — ruling 5

If you pay the evoke cost, you can have the creature's own triggered ability resolve before the evoke triggered ability. You can cast spells after that ability resolves but before you have to sacrifice the creature.

Subtlety : règles, fonctionnement et interactions (MTG)

Subtlety 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

Flash Flying When this creature enters, choose up to one target creature spell or planeswalker spell. Its owner puts it on their choice of the top or bottom of their library. Evoke—Exile a blue card from your hand.

How it works : Subtlety

Original English text — Wizards of the Coast / Scryfall

#1June 18, 2021· Wizards of the Coast
Subtlety's triggered ability targets a spell on the stack. It can't target creatures or planeswalkers on the battlefield.
No other card is named in this ruling.
#2June 18, 2021· Wizards of the Coast
A spell that's put into its owner's library doesn't resolve, but it isn't countered. This will work on spells that say they can't be countered.
No other card is named in this ruling.
#3June 18, 2021· Wizards of the Coast
The owner of the spell is the one who chooses whether it goes on the top or bottom of their library. All players will know this information.
No other card is named in this ruling.
#4June 18, 2021· Wizards of the Coast
To determine the total cost of a spell, start with the mana cost or alternative cost you're paying (such as an evoke cost), add any cost increases, then apply any cost reductions. The mana value of the spell is determined by only its mana cost, no matter what the total cost to cast that spell was.
No other card is named in this ruling.
#5June 18, 2021· Wizards of the Coast
If you pay the evoke cost, you can have the creature's own triggered ability resolve before the evoke triggered ability. You can cast spells after that ability resolves but before you have to sacrifice the creature.
No other card is named in this ruling.