Ruins of Oran-Rief — ruling 1

The target of the last ability didn’t necessarily have to be a colorless creature as it entered the battlefield, provided it entered the battlefield during that turn. However, it does have to be a colorless creature to be a legal target of the ability.

Ruins of Oran-Rief : règles, fonctionnement et interactions (MTG)

Ruins of Oran-Rief 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 land enters tapped. : Add . ( represents colorless mana.) : Put a +1/+1 counter on target colorless creature that entered this turn.

How it works : Ruins of Oran-Rief

Original English text — Wizards of the Coast / Scryfall

#1January 22, 2016· Wizards of the Coast
The target of the last ability didn’t necessarily have to be a colorless creature as it entered the battlefield, provided it entered the battlefield during that turn. However, it does have to be a colorless creature to be a legal target of the ability.
No other card is named in this ruling.