Marauding Blight-Priest

• WWizards of the Coast2024-11-08
  Official Ruling
  Marauding Blight-Priest's ability triggers just once for each life-gaining event, whether it's 1 life from Dazzling Angel or 4 life from Apothecary Stomper.
• WWizards of the Coast2024-11-08
  Official Ruling
  If you gain an amount of life "for each" of something or "equal to the number" of something, that life is gained as one event and Marauding Blight-Priest's ability will trigger only once.
• WWizards of the Coast2024-11-08
  Official Ruling
  In a Two-Headed Giant game, life gained by your teammate won't cause Marauding Blight-Priest's ability to trigger, even though it caused your team's life total to increase.
• WWizards of the Coast2024-11-08
  Official Ruling
  Each creature with lifelink dealing combat damage causes a separate life-gaining event. For example, if two creatures you control with lifelink deal combat damage at the same time, Marauding Blight-Priest's ability will trigger twice. However, if a single creature you control with lifelink deals combat damage to multiple creatures, players, planeswalkers, and/or battles at the same time (perhaps because it has trample or was blocked by more than one creature), the ability will trigger only once.

Rulings via Scryfall