Ethersworn Shieldmage — ruling 1

When Ethersworn Shieldmage’s triggered ability resolves, it doesn’t lock in which permanents will be affected. For the rest of the turn, any time damage would be dealt to a permanent, check whether it’s an artifact creature at that time. If it is, that damage is prevented.

Ethersworn Shieldmage : règles, fonctionnement et interactions (MTG)

Ethersworn Shieldmage 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 When this creature enters, prevent all damage that would be dealt to artifact creatures this turn.

How it works : Ethersworn Shieldmage

Original English text — Wizards of the Coast / Scryfall

#1May 1, 2009· Wizards of the Coast
When Ethersworn Shieldmage’s triggered ability resolves, it doesn’t lock in which permanents will be affected. For the rest of the turn, any time damage would be dealt to a permanent, check whether it’s an artifact creature at that time. If it is, that damage is prevented.
No other card is named in this ruling.