Keyword Spotlight – Brainstorm

Welcome to the 9th CX’s spotlight on keywords! This miniseries is geared toward newer players to go in-depth on the many keyword abilities in Weiss Schwarz.


If you play WS long enough, you will inevitably encounter the game’s most difficult keyword – brainstorm! Usually, brainstorm reveals the top four cards of the deck, and puts them into the waiting room, and triggers an effect for each CX revealed. However, the keyword is applied to any effect that reveals X cards from the top of the deck, puts them into the waiting room, and applies an effect based on if a CX is revealed or not.

Rules tip: If you have fewer than 4 (or whatever number is asked) cards left in the deck, you reveal as many as you can, refresh the deck, set the refresh counter to one, reveal cards until you have seen as many as the effect requires, finish resolving the effect, and then apply the refresh penalty.

The triggered effects from cards with brainstorm can vary wildly. Some allow you to return characters from the waiting room to the hand then discard a card. Others let you search your deck for a character of a certain characteristic. Some add power, some add soul, and some just let you draw cards. But the largest effect brainstorm can have is denying damage that your opponent could deal to you on their following turn with attacks.

Math! … Again??

Yes indeed, math strikes again but in a more hard-to-find way. For the sake of this exercise, we’ll assume that the brainstorm effect is always for the top 4 cards of the deck.

Let’s take a look at this table.

Brainstorm Equals 1

In this table, we have the probabilities of finding one CX in the top 4 cards of the deck, where there are 1-50 cards left in the deck, and 1-8 CXs remaining in the deck. The spots highlighted in red show the percentages where the cards revealed will have a less than 50% chance to have a CX among them (and the overall effect will be denying damage), and the spots highlighted in green show the percentages where the cards revealed will have a greater than 50% chance to have a CX among them (and the overall effect will be achieving the effect described by the brainstorming card).

Upon further inspection though, this table does not work.

Well then, why show this table if it’s wrong?

To make a point, of course!

Instead of looking at situations where only one CX is revealed via brainstorm, we have to look at the cumulative hypergeometric probability. That is, we have to account for the chances that one or more CX will be revealed with the brainstorm effect, rather than just one.

So what does the real table look like? Well, thanks to, I was able to find the cumulative hypergeometric probabilities and make this one here:

Brainstorm is Greater Than Or Equal to 1

Again, the cells highlighted in green show where revealing a CX is favorable (effect will likely trigger), and the cells highlighted in red show where revealing a CX is unfavorable (effect will likely be denying damage). Let’s walk through the chart to interpret the data.

With 8 CXs left, brainstorms are at a 51% chance or better to reveal a CX. This means that no brainstorm effect at 8 CXs remaining can be counted on to be efficient in denying damage.

Now there has to be a better way to express this without typing it all out…

Brainstorm ShortChart

Much better! This little table here gives you the best times to brainstorm for the effect desired. Note the number of cards remaining on the left, as the numbers are not evenly spaced. For example, at 32 cards left, if you have 8 CXs remaining, you’ll most likely reveal one or more CXs in a brainstorm, but with 4 or fewer, will more likely be denying your opponent 4 damage.

Keep in mind that this table is not usable during a game because of the game’s strict no-notes policy. Please go ahead and print and/or save the tables for your personal use (just make sure the blog credit stays on the image!).

Questions? Comments? Send an email to theninthcx AT gmail DOT com!