Forerunner of the Heralds — ruling 1

If an effect refers to a “[subtype] spell” or “[subtype] card,” it refers only to a spell or card that has that subtype. For example, March of the Drowned is a card that benefits Pirates and features Pirates in its illustration, but it isn’t a Pirate card.

Forerunner of the Heralds : règles, fonctionnement et interactions (MTG)

Forerunner of the Heralds 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

When this creature enters, you may search your library for a Merfolk card, reveal it, then shuffle and put that card on top. Whenever another Merfolk you control enters, put a +1/+1 counter on this creature.

How it works : Forerunner of the Heralds

Original English text — Wizards of the Coast / Scryfall

#1January 19, 2018· Wizards of the Coast
If an effect refers to a “[subtype] spell” or “[subtype] card,” it refers only to a spell or card that has that subtype. For example, March of the Drowned is a card that benefits Pirates and features Pirates in its illustration, but it isn’t a Pirate card.
No other card is named in this ruling.