Sword of Fire and IceSword of Fire and Ice | art by Chris Rahn

Hello, data enthusiasts, and welcome to this overview of the math behind the new Fire and Ice data articles. In this series, we'll we dive into the recent card-playing trends within a given commander and identify the biggest movers as defined as:

Cards that are either significantly increasing or decreasing in usage with a given commander relative to other cards played with that commander over the most recent six months.

This article will provide an overview of the math behind identifying these "fiery" (trending up) and "icy" (trending down) cards.

Why a given card might be fiery or icy, however, is up to interpretation, and we look forward to speculating wildly in our Fire and Ice series!

Overview of the Math

We start by looking at all cards that are played with each commander aside from those that are very rare (<2.5% of decks) or very ubiquitous (> 97.5% of decks).

We calculate the weekly usage of these cards as a percentage of all decks for each given commander for the past six months.

Then, we determine the average change from week to week and summarize the data with a single "extremeness" score (also known as a z-score) as follows:

where x = average weekly change in card usage (% of decks for this commander)

We currently identify those cards with extremeness > 2 as "fiery", or having a high Fire Score, and those with extremeness < -2 as "icy", or having a low Ice Score.

Using these extremeness scores allows us to control for the unique deck-building behavior of each commander rather than using a fixed threshold of average change to identify big movers.

For example, a commander that has been around for a while that has fairly predictable deck-building (e.g. The Ur-DragonThe Ur-Dragon) will see very little movement in the usage of each card over time compared to a commander that has more flexibility in its play (e.g. Omnath, Locus of RageOmnath, Locus of Rage).

This might mean a relatively small uptick for a card played with The Ur-Dragon will have the same Fire score as a card with a large uptick with Omnath.

An Example

Let's take a look at card usage in Urza, Lord High ArtificerUrza, Lord High Artificer decks over the six month period from December 24, 2024 to June 24, 2025.

This plot shows a time series of the weekly usage of all 378 qualifying cards across this commander's decks.

Another way we can look at the data is relative to the start of the time period.

Here, we see certain cards emerge more clearly as "big movers".

If we calculate the average weekly change for each card and look at the distribution across all qualifying Urza cards, we see roughly a bell curve with some extreme values that get flagged as being fiery or icy:

Let's once again plot the relative time series graph, this time highlighting the identified fiery and icy cards.

We can see that these cards clearly have exhibited more extreme changes over the time period than the cards identified as stable:

The following table shows which cards were identified as fiery and icy, along with their average weekly changes, extremeness score, and the number of decks they were played in over the six month time period.

Repurposing BayRepurposing Bay takes the cake for fieriest card, with a Fire score of 5.85, and Etherium SculptorEtherium Sculptor as the iciest card, with an Ice score of -3.54.

The top four fieriest cards (Repurposing BayRepurposing Bay, Mistrise VillageMistrise Village, Unstoppable PlanUnstoppable Plan, Ugin, Eye of the StormsUgin, Eye of the Storms) were released in the examined six-month period and were able to achieve high Fire Scores largely due to starting at 0% usage.

Not all newly released cards will show up as fiery if they aren't an obviously good fit for the given commander, but it is a good thing to be aware of.

Icy cards are often less explicable as we often see Commander staples showing up icy; this may be due to potential replacements coming on the scene or any of a number of other reasons. 

What to Expect in the Fire and Ice Series

In Fire and Ice, we'll highlight commanders with intriguing fiery and icy cards and comment on why we believe each card is trending up or down.

We will also provide the Fire and Ice score of each card discussed along with graphs of the relative weekly usage of each card over the specified time period.

Starting today, you'll find brand new Fire and Ice articles out every Friday on EDHREC!