Pain Magnification — ruling 1

This triggers only if all 3 or more damage is dealt at the same time. It doesn’t trigger if damage that adds up to 3 or more is dealt at different times by the same source.

Pain Magnification — ruling 2

If a source deals 3 or more damage to multiple opponents at the same time, this ability will trigger once for each of those opponents. They will each have to discard a card.

Pain Magnification : règles, fonctionnement et interactions (MTG)

Pain Magnification 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 an opponent is dealt 3 or more damage by a single source, that player discards a card.

How it works : Pain Magnification

Original English text — Wizards of the Coast / Scryfall

#1May 1, 2006· Wizards of the Coast
This triggers only if all 3 or more damage is dealt at the same time. It doesn’t trigger if damage that adds up to 3 or more is dealt at different times by the same source.
No other card is named in this ruling.
#2May 1, 2006· Wizards of the Coast
If a source deals 3 or more damage to multiple opponents at the same time, this ability will trigger once for each of those opponents. They will each have to discard a card.
No other card is named in this ruling.