Mogg Salvage — ruling 1

To cast Mogg Salvage without paying its mana cost, any opponent may control an Island, not just the one who controls the target artifact.

Mogg Salvage — ruling 2

Who controls what lands is important only as you cast Mogg Salvage. Once it has been cast, you no longer controlling a Mountain or each opponent no longer controlling any Islands won't affect Mogg Salvage.

Mogg Salvage — ruling 3

Casting a spell without paying its mana cost has no effect on its mana value. Mogg Salvage's mana value is always 3.

Mogg Salvage — ruling 4

You don't sacrifice Nevinyrral's Disk to activate its ability. It's destroyed as part of the ability's resolution if it's still on the battlefield. If an effect gives Nevinyrral's Disk indestructible or regenerates it, it stays on the battlefield.

Mogg Salvage : règles, fonctionnement et interactions (MTG)

Mogg Salvage 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

If an opponent controls an Island and you control a Mountain, you may cast this spell without paying its mana cost. Destroy target artifact.

How it works : Mogg Salvage

Original English text — Wizards of the Coast / Scryfall

#1June 18, 2021· Wizards of the Coast
To cast Mogg Salvage without paying its mana cost, any opponent may control an Island, not just the one who controls the target artifact.
No other card is named in this ruling.
#2June 18, 2021· Wizards of the Coast
Who controls what lands is important only as you cast Mogg Salvage. Once it has been cast, you no longer controlling a Mountain or each opponent no longer controlling any Islands won't affect Mogg Salvage.
No other card is named in this ruling.
#3June 18, 2021· Wizards of the Coast
Casting a spell without paying its mana cost has no effect on its mana value. Mogg Salvage's mana value is always 3.
No other card is named in this ruling.
#4June 18, 2021· Wizards of the Coast
You don't sacrifice Nevinyrral's Disk to activate its ability. It's destroyed as part of the ability's resolution if it's still on the battlefield. If an effect gives Nevinyrral's Disk indestructible or regenerates it, it stays on the battlefield.
No other card is named in this ruling.