Bad Moon 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

Black creatures get +1/+1.

Complete guide

Bad Moon is a classic black enchantment that provides a continuous boost to your dark legions. It is a simple yet effective way to amplify the power and toughness of every black creature on the battlefield. Whether you are swarming the board or building a single threat, this card ensures your forces hit harder and stay alive longer.

What It Does

Bad Moon is a static effect that grants a +1/+1 bonus to all black creatures currently on the battlefield. Because the ability does not target, it affects creatures regardless of Ward or Hexproof. Crucially, this effect is symmetrical; it buffs your black creatures and those owned by your opponents, so be mindful of the board state before casting it.

How It Resolves Step by Step

First, you cast Bad Moon by paying its mana cost of one generic and one black mana. Once it resolves and enters the battlefield, its continuous effect immediately applies to all eligible creatures. There is no trigger to respond to; as soon as a creature is considered black, it gains +1/+1. If a creature loses its black color or leaves the battlefield, the bonus vanishes instantly. Similarly, if Bad Moon is destroyed, all creatures lose the bonus immediately.

Common Mistakes

A frequent oversight is forgetting that Bad Moon affects all black creatures, not just yours. If you are playing against another black deck, you might accidentally help your opponent win a combat trade. Another mistake involves timing; since this is an enchantment and not an instant, you cannot use it as a 'combat trick' to surprise an opponent during the declare blockers step unless you have a way to cast it with Flash.

When to Play It

Bad Moon is most effective in 'Black Weenie' decks or token strategies where you have a high density of small black creatures. By increasing their stats, you move them out of range of toughness-based board wipes like Infest or Cower in Fear. It is best played early in the game to maximize the extra damage dealt over multiple combat phases.

Interaction examples

Boosting Mercenary Tokens

Black Market Connections

You have Bad Moon on the battlefield. At the start of your main phase, Black Market Connections triggers, and you choose 'Hire a Mercenary.' You create a 3/2 colorless Shapeshifter token. However, because the token has Changeling, it is every creature type, but it remains colorless. Therefore, Bad Moon does not grant it +1/+1 unless another effect makes the token black.

Global Power Scaling

Phyrexian Arena

With Phyrexian Arena ensuring you draw extra cards every turn, you quickly fill your hand with low-cost black creatures. When you play Bad Moon, every creature you have deployed since the start of the game receives an immediate power boost. This synergy allows you to maintain card advantage while ensuring the creatures you draw are significant threats on the table.

Guide written with AI from the official text and rulings. Official English text prevails.