Harness the Storm — ruling 1

You must choose a target for Harness the Storm’s ability (if one exists) immediately after you’ve cast an instant or sorcery spell. There’s no way for that spell to be countered and then targeted by Harness the Storm once it’s in the graveyard.

Harness the Storm — ruling 2

You choose whether to cast the targeted card as the ability resolves. You can’t wait to cast it later, and there’s no way for your opponents to set up a situation where you have to cast the card but don’t want to.

Harness the Storm — ruling 3

If the spell you cast from your hand is countered in response to Harness the Storm’s triggered ability, you can still cast the target card while the ability is resolving.

Harness the Storm — ruling 4

Because you’re paying the spell’s costs, you can pay alternative costs, such as awaken costs and surge costs from the Battle for Zendikar block. You can also pay additional costs, such as kicker costs. If the card has a mandatory additional cost, like Lightning Axe, you must pay it to cast the card.

Harness the Storm — ruling 5

The spell you cast from your graveyard can target the spell you cast from your hand.

Harness the Storm — ruling 6

The spell you cast from your graveyard resolves before the spell you cast from your hand. It’s put into your graveyard as it resolves.

Harness the Storm : règles, fonctionnement et interactions (MTG)

Harness the Storm 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

Whenever you cast an instant or sorcery spell from your hand, you may cast target card with the same name as that spell from your graveyard. (You still pay its costs.)

How it works : Harness the Storm

Original English text — Wizards of the Coast / Scryfall

#1April 8, 2016· Wizards of the Coast
You must choose a target for Harness the Storm’s ability (if one exists) immediately after you’ve cast an instant or sorcery spell. There’s no way for that spell to be countered and then targeted by Harness the Storm once it’s in the graveyard.
No other card is named in this ruling.
#2April 8, 2016· Wizards of the Coast
You choose whether to cast the targeted card as the ability resolves. You can’t wait to cast it later, and there’s no way for your opponents to set up a situation where you have to cast the card but don’t want to.
No other card is named in this ruling.
#3April 8, 2016· Wizards of the Coast
If the spell you cast from your hand is countered in response to Harness the Storm’s triggered ability, you can still cast the target card while the ability is resolving.
No other card is named in this ruling.
#4April 8, 2016· Wizards of the Coast
Because you’re paying the spell’s costs, you can pay alternative costs, such as awaken costs and surge costs from the Battle for Zendikar block. You can also pay additional costs, such as kicker costs. If the card has a mandatory additional cost, like Lightning Axe, you must pay it to cast the card.
No other card is named in this ruling.
#5April 8, 2016· Wizards of the Coast
The spell you cast from your graveyard can target the spell you cast from your hand.
No other card is named in this ruling.
#6April 8, 2016· Wizards of the Coast
The spell you cast from your graveyard resolves before the spell you cast from your hand. It’s put into your graveyard as it resolves.
No other card is named in this ruling.