Mentor's Guidance — ruling 1

The triggered ability will trigger when you cast Mentor's Guidance no matter what permanents you control. As that ability tries to resolve, it will check to see if you control at least one permanent with the listed type or subtypes. If you do, Mentor's Guidance will be copied once, not once for each of those permanents. If you don't control a qualifying permanent at that time, the triggered ability won't resolve and it won't copy Mentor's Guidance.

Mentor's Guidance : règles, fonctionnement et interactions (MTG)

Mentor's Guidance 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 you cast this spell, copy it if you control a planeswalker, Cleric, Druid, Shaman, Warlock, or Wizard. Scry 1, then draw a card.

How it works : Mentor's Guidance

Original English text — Wizards of the Coast / Scryfall

#1April 16, 2021· Wizards of the Coast
The triggered ability will trigger when you cast Mentor's Guidance no matter what permanents you control. As that ability tries to resolve, it will check to see if you control at least one permanent with the listed type or subtypes. If you do, Mentor's Guidance will be copied once, not once for each of those permanents. If you don't control a qualifying permanent at that time, the triggered ability won't resolve and it won't copy Mentor's Guidance.
No other card is named in this ruling.