Herald of Kozilek — ruling 1

If a card loses devoid, it will still be colorless. This is because effects that change an object's color (like the one created by devoid) are considered before the object loses devoid.

Herald of Kozilek — ruling 2

Herald of Kozilek's last ability doesn't change the mana cost or mana value of any spell. It changes only the total cost you actually pay.

Herald of Kozilek — ruling 3

Herald of Kozilek's last ability can't reduce the amount of colored mana you pay for a spell. It reduces only the generic component of that mana cost.

Herald of Kozilek — ruling 4

If there are additional costs to cast a spell, or if the cost to cast a spell is increased by an effect, apply those increases before applying cost reductions.

Herald of Kozilek — ruling 5

The cost reduction can apply to alternative costs.

Herald of Kozilek — ruling 6

If a colorless spell you cast has {X} in its mana cost, you choose the value of X before calculating the spell's total cost. For example, if that spell's mana cost is {X}, you could choose 5 as the value of X and pay {4} to cast the spell.

Herald of Kozilek — ruling 7

Cards with devoid use frames that are variations of the transparent frame traditionally used for Eldrazi. The top part of the card features some color over a background based on the texture of the hedrons that once imprisoned the Eldrazi. This coloration is intended to aid deckbuilding and game play.

Herald of Kozilek — ruling 8

A card with devoid is just colorless. It's not colorless and the colors of mana in its mana cost.

Herald of Kozilek : règles, fonctionnement et interactions (MTG)

Herald of Kozilek 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

Devoid (This card has no color.) Colorless spells you cast cost less to cast.

Complete guide

Herald of Kozilek is a cornerstone for Eldrazi and artifact strategies, providing a significant tempo advantage by making your colorless spells cheaper. Despite having Blue and Red in its mana cost, its Devoid ability ensures it remains colorless in all zones, fitting perfectly into decks that care about colorless synergies. This Eldrazi Drone turns your mid-game plays into early-game threats by shaving off generic mana costs.

Understanding Devoid and Cost Reduction

Herald of Kozilek possesses the Devoid keyword, which means it is colorless regardless of the mana required to cast it. This applies in your hand, library, and graveyard. Its primary utility comes from its static ability, which reduces the cost of colorless spells you cast by {1}. This reduction applies to any spell that lacks colors, including most artifacts, Eldrazi, and spells with the Devoid keyword.

The Step-by-Step Casting Process

When you cast a colorless spell while Herald of Kozilek is on the battlefield, you follow a specific order to determine the cost. First, you announce the spell and choose a value for {X} if applicable. Second, you apply any cost increases or additional costs (like Kicker). Third, you apply cost reductions, such as the {1} discount from Herald of Kozilek. Finally, the total cost is locked in, and you pay the mana. Note that this reduction only applies to the generic mana component; it cannot reduce colored mana requirements.

Common Mistakes to Avoid

A frequent misconception is that Herald of Kozilek changes the mana value (formerly converted mana cost) of your spells. It does not; it only changes the 'Total Cost' paid. Another error is attempting to use the discount on colored spells that contain colorless mana in their costs; the spell itself must be colorless for the discount to apply. Lastly, remember that even if an effect removes the Devoid ability from Herald of Kozilek, it remains colorless due to how layer-based effects are processed in Magic rules.

When to Play Herald of Kozilek

Herald of Kozilek is best played early to maximize the cumulative mana saved over several turns. Because it has a defensive 2/4 stat line, it serves as a reliable blocker against aggressive decks while you build your board. It is particularly potent in decks featuring heavy hitters or multiple spells per turn, as the {1} discount applies to every colorless spell you cast, not just the first one each turn.

Interaction examples

Accelerating Artifact Utility

Solemn Simulacrum

With Herald of Kozilek on the battlefield, you decide to cast Solemn Simulacrum. The normal cost of Solemn Simulacrum is {4}. Because it is an artifact creature and therefore colorless, Herald of Kozilek applies a {1} reduction. You pay only {3} to cast the spell. When it enters, you still get to search for a basic land, effectively ramping your mana even further for a lower initial investment.

Doubling Down on Type Synergies

Roaming Throne

You cast Roaming Throne while controlling Herald of Kozilek. Roaming Throne is a colorless artifact creature, so its cost is reduced from {4} to {3}. As it enters, you can choose 'Eldrazi' as the creature type. Now, not only did you cast the Throne for cheaper, but any triggered abilities of Herald of Kozilek or other Eldrazi Drones you control will trigger an additional time.

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

How it works : Herald of Kozilek

Original English text — Wizards of the Coast / Scryfall

#1August 25, 2015· Wizards of the Coast
If a card loses devoid, it will still be colorless. This is because effects that change an object's color (like the one created by devoid) are considered before the object loses devoid.
No other card is named in this ruling.
#2August 25, 2015· Wizards of the Coast
Herald of Kozilek's last ability doesn't change the mana cost or mana value of any spell. It changes only the total cost you actually pay.
No other card is named in this ruling.
#3August 25, 2015· Wizards of the Coast
Herald of Kozilek's last ability can't reduce the amount of colored mana you pay for a spell. It reduces only the generic component of that mana cost.
No other card is named in this ruling.
#4August 25, 2015· Wizards of the Coast
If there are additional costs to cast a spell, or if the cost to cast a spell is increased by an effect, apply those increases before applying cost reductions.
No other card is named in this ruling.
#5August 25, 2015· Wizards of the Coast
The cost reduction can apply to alternative costs.
No other card is named in this ruling.
#6August 25, 2015· Wizards of the Coast
If a colorless spell you cast has in its mana cost, you choose the value of X before calculating the spell's total cost. For example, if that spell's mana cost is , you could choose 5 as the value of X and pay to cast the spell.
No other card is named in this ruling.
#7August 25, 2015· Wizards of the Coast
Cards with devoid use frames that are variations of the transparent frame traditionally used for Eldrazi. The top part of the card features some color over a background based on the texture of the hedrons that once imprisoned the Eldrazi. This coloration is intended to aid deckbuilding and game play.
No other card is named in this ruling.
#8August 25, 2015· Wizards of the Coast
A card with devoid is just colorless. It's not colorless and the colors of mana in its mana cost.
No other card is named in this ruling.
#9August 25, 2015· Wizards of the Coast
Other cards and abilities can give a card with devoid color. If that happens, it's just the new color, not that color and colorless.
No other card is named in this ruling.
#10August 25, 2015· Wizards of the Coast
Devoid works in all zones, not just on the battlefield.
No other card is named in this ruling.