Rhonas's Monument — ruling 1

The triggered ability of Rhonas's Monument can't target the creature spell that caused it to trigger.

Rhonas's Monument — ruling 2

Each Monument has one ability that reduces the cost of creature spells of a certain color, and a triggered ability that triggers whenever you cast any creature spell—not just a creature spell of that color.

Rhonas's Monument — ruling 3

A creature spell that's multiple colors is each of those colors. For example, Ahn-Crop Champion is a white creature and a green creature, so it can benefit from either Oketra's Monument or Rhonas's Monument—or both at once.

Rhonas's Monument — ruling 4

To determine the total cost of a creature spell, start with the mana cost or alternative cost you're paying, add any cost increases, then apply any cost reductions. The mana value of the creature remains unchanged, no matter what the total cost to cast it was.

Rhonas's Monument — ruling 5

Each Monument's triggered ability triggers as the creature spell is cast and resolves before that creature spell resolves. The ability will resolve even if that creature spell is countered.

Rhonas's Monument : règles, fonctionnement et interactions (MTG)

Rhonas's Monument 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

Green creature spells you cast cost less to cast. Whenever you cast a creature spell, target creature you control gets +2/+2 and gains trample until end of turn.

How it works : Rhonas's Monument

Original English text — Wizards of the Coast / Scryfall

#1April 18, 2017· Wizards of the Coast
The triggered ability of Rhonas's Monument can't target the creature spell that caused it to trigger.
No other card is named in this ruling.
#2April 18, 2017· Wizards of the Coast
Each Monument has one ability that reduces the cost of creature spells of a certain color, and a triggered ability that triggers whenever you cast any creature spell—not just a creature spell of that color.
No other card is named in this ruling.
#3April 18, 2017· Wizards of the Coast
A creature spell that's multiple colors is each of those colors. For example, Ahn-Crop Champion is a white creature and a green creature, so it can benefit from either Oketra's Monument or Rhonas's Monument—or both at once.
No other card is named in this ruling.
#4April 18, 2017· Wizards of the Coast
To determine the total cost of a creature spell, start with the mana cost or alternative cost you're paying, add any cost increases, then apply any cost reductions. The mana value of the creature remains unchanged, no matter what the total cost to cast it was.
No other card is named in this ruling.
#5April 18, 2017· Wizards of the Coast
Each Monument's triggered ability triggers as the creature spell is cast and resolves before that creature spell resolves. The ability will resolve even if that creature spell is countered.
No other card is named in this ruling.