Geistblast — ruling 1

Geistblast's ability can copy any instant or sorcery spell, not just one with targets.

Geistblast — ruling 2

When Geistblast's ability resolves, it creates a copy of the instant or sorcery spell. The copy is created on the stack, so it's not "cast." Abilities that trigger when a player casts a spell won't trigger. The copy will then resolve like a normal spell, before the original spell resolves but after players get a chance to cast spells and activate abilities.

Geistblast — ruling 3

The copy will have the same targets as the spell it's copying unless you choose new ones. You may change any number of the targets, including all of them or none of them. If, for one of the targets, you can't choose a new legal target, then it remains unchanged (even if the current target is illegal).

Geistblast — ruling 4

If the spell being copied is modal (that is, it says "Choose one —" or the like), the copy will have the same mode. You can't choose a different one.

Geistblast — ruling 5

If the spell being copied has an X whose value was determined as it was cast (like Avacyn's Judgment's madness cost has), the copy will have the same value of X.

Geistblast — ruling 6

If the spell has damage divided as it was cast (also like Avacyn's Judgment), the division can't be changed (although the targets receiving that damage still can).

Geistblast — ruling 7

If an alternative cost was paid for the spell, such as its madness cost or surge cost, the same alternative cost is considered to have been paid for the copy.

Geistblast : règles, fonctionnement et interactions (MTG)

Geistblast 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

Geistblast deals 2 damage to any target. , Exile this card from your graveyard: Copy target instant or sorcery spell you control. You may choose new targets for the copy.

How it works : Geistblast

Original English text — Wizards of the Coast / Scryfall

#1April 8, 2016· Wizards of the Coast
Geistblast's ability can copy any instant or sorcery spell, not just one with targets.
No other card is named in this ruling.
#2April 8, 2016· Wizards of the Coast
When Geistblast's ability resolves, it creates a copy of the instant or sorcery spell. The copy is created on the stack, so it's not "cast." Abilities that trigger when a player casts a spell won't trigger. The copy will then resolve like a normal spell, before the original spell resolves but after players get a chance to cast spells and activate abilities.
No other card is named in this ruling.
#3April 8, 2016· Wizards of the Coast
The copy will have the same targets as the spell it's copying unless you choose new ones. You may change any number of the targets, including all of them or none of them. If, for one of the targets, you can't choose a new legal target, then it remains unchanged (even if the current target is illegal).
No other card is named in this ruling.
#4April 8, 2016· Wizards of the Coast
If the spell being copied is modal (that is, it says "Choose one —" or the like), the copy will have the same mode. You can't choose a different one.
No other card is named in this ruling.
#5April 8, 2016· Wizards of the Coast
If the spell being copied has an X whose value was determined as it was cast (like Avacyn's Judgment's madness cost has), the copy will have the same value of X.
No other card is named in this ruling.
#6April 8, 2016· Wizards of the Coast
If the spell has damage divided as it was cast (also like Avacyn's Judgment), the division can't be changed (although the targets receiving that damage still can).
No other card is named in this ruling.
#7April 8, 2016· Wizards of the Coast
If an alternative cost was paid for the spell, such as its madness cost or surge cost, the same alternative cost is considered to have been paid for the copy.
No other card is named in this ruling.