Volcanic Offering — ruling 1

Unlike the other Offerings, you choose the opponents for Volcanic Offering as you cast the spell because those players are involved in choosing the spell’s targets.

Volcanic Offering — ruling 2

The chosen opponent for each effect may choose the same target nonbasic land or creature you don’t control that you did.

Volcanic Offering — ruling 3

You may choose the same opponent for each of the effects, or you may choose different opponents. None of the affected players are targets of the spell.

Volcanic Offering : règles, fonctionnement et interactions (MTG)

Volcanic Offering 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

Destroy target nonbasic land you don't control and target nonbasic land of an opponent's choice you don't control. Volcanic Offering deals 7 damage to target creature you don't control and 7 damage to target creature of an opponent's choice you don't control.

How it works : Volcanic Offering

Original English text — Wizards of the Coast / Scryfall

#1November 7, 2014· Wizards of the Coast
Unlike the other Offerings, you choose the opponents for Volcanic Offering as you cast the spell because those players are involved in choosing the spell’s targets.
No other card is named in this ruling.
#2November 7, 2014· Wizards of the Coast
The chosen opponent for each effect may choose the same target nonbasic land or creature you don’t control that you did.
No other card is named in this ruling.
#3November 7, 2014· Wizards of the Coast
You may choose the same opponent for each of the effects, or you may choose different opponents. None of the affected players are targets of the spell.
No other card is named in this ruling.