River Serpent — ruling 1

Once River Serpent has attacked, it will remain in combat even if the number of cards in your graveyard becomes four or fewer.

River Serpent : règles, fonctionnement et interactions (MTG)

River Serpent 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

This creature can't attack unless there are five or more cards in your graveyard. Cycling (, Discard this card: Draw a card.)

How it works : River Serpent

Original English text — Wizards of the Coast / Scryfall

#1April 18, 2017· Wizards of the Coast
Once River Serpent has attacked, it will remain in combat even if the number of cards in your graveyard becomes four or fewer.
No other card is named in this ruling.