Meanders Guide — ruling 1

If a card in a graveyard has {X} in its mana cost, X is 0 for the purpose of determining its mana value.

Meanders Guide — ruling 2

You don't choose a target for Meanders Guide's ability at the time it triggers. Rather, a second "reflexive" ability triggers when you tap another untapped Merfolk you control this way. You choose a target for that ability as it goes on the stack. Each player may respond to this triggered ability as normal.

Meanders Guide : règles, fonctionnement et interactions (MTG)

Meanders Guide 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 this creature attacks, you may tap another untapped Merfolk you control. When you do, return target creature card with mana value 3 or less from your graveyard to the battlefield.

How it works : Meanders Guide

Original English text — Wizards of the Coast / Scryfall

#1November 17, 2025· Wizards of the Coast
If a card in a graveyard has in its mana cost, X is 0 for the purpose of determining its mana value.
No other card is named in this ruling.
#2November 17, 2025· Wizards of the Coast
You don't choose a target for Meanders Guide's ability at the time it triggers. Rather, a second "reflexive" ability triggers when you tap another untapped Merfolk you control this way. You choose a target for that ability as it goes on the stack. Each player may respond to this triggered ability as normal.
No other card is named in this ruling.