Challenge Your Playtesting – Welcome to the Thunderbowl

Gone Fishing

Hi, EDHREC friends! Please excuse this interruption from the regular Challenge the Stats article series for something completely different. Some of you may have noticed that I had an odd poll at the end of my last article asking how people playtest their decks. From almost 1,000 responses, over 80% of Commander players “goldfish” their decks in some way. If you’re in that 80%, this article is for you.

I playtest, or “goldfish”, my Commander decks pretty often. I find it meditative to zone out and flip over my colorful pieces of cardboard. I do this to make sure that my decks run smoothly and also get better at piloting them, so when I’m in-game I can focus more on having fun and less on planning my lines of play. I usually play decks by themselves, either in paper or using a deckbuilding website’s “playtest” feature.

However, this doesn’t provide us with the challenges we’d see in a real game, and once I get my deck’s engine going, I usually get bored and shuffle up. I could battle two or more decks against each other (about 18% of poll responders do this), but that seems like too much of a hassle to me. So, I started developing a playtesting format that would let me play decks by themselves while providing some interaction and keeping my interest through a whole simulation until I win or lose.

The idea is simple: we use a D20 to represent actions made by our opponents. Each side of the D20 represents a spell or action that our opponents take. Most of them are bad, but not all of them may affect our current board state. For example, if we roll a 3, which represents a Vandalblast, we might get off easy if we have few or no artifacts. This method can be used either in paper or alongside a deckbuilding website’s playtesting feature.

Why is this helpful? It’s easy for our deck to do well with no interaction. Adding some challenge tells us how our deck works when disrupted. Also, adding the stakes of winning or losing helps us remember triggers and sequence plays correctly.

Let’s check out the rules.

Welcome to the Thunderbowl

You and one “opponent” each start at 40 life. You can deal damage to your “opponent” through combat or spells, and they can cast disruptive spells or deal damage to you on their turn. If your opponent’s life total hits 0 while you still have a positive life total, you win; otherwise, you lose.

What you need

  • Dice (at least one D20, or this website)
  • A way to keep track of our health and one “opponent’s” health (dice, paper, or phone app)
  • 100 cards
  • Can-do attitude

Opponent’s Turn: Roll a D20

1-8 is counterable

Destroy all nonland permanents – Planar Cleansing

2 Destroy all creatures – Day of Judgment

3 Destroy all artifacts – Vandalblast

4 Destroy all enchantments – Tempest of Light

5 Sacrifice highest-power creature and take 2 damage – Crackling Doom

6 Return each commander to command zone – Leadership Vacuum

7 Destroy single best artifact (you choose, honor system) – Abrade

Destroy single best enchantment (you choose, honor system) – Esper Charm

9-20 is uncounterable, but may be prevented

9 If you control four or more lands, destroy single best non-basic land (you choose, honor system) – Tectonic Edge

10 Take 10 damage – Attacked by an unblockable 10/10, (may be prevented with a removal spell, fog, prevent damage, etc.)

11  Take 1 direct damage

12 Take 2 direct damage

13 Take 3 direct damage

14  Take 4 direct damage

15 Take 5 direct damage

16  Take 6 direct damage

17 Take 7 direct damage

18 Take 8 direct damage

19  Exile all graveyards – Scavenger Grounds

20 Draw a card – Temple Bell

**If you control a planeswalker, roll an additional D20 for each one to see if it gets attacked. On a 1-10, it gets attacked by one unblockable creature with a D6 worth of power and toughness.

Your Turn

Roll a D20 for each non-evasive creature that attacks; the number indicates the result:

1-2 Opponent responds! Destroy target attacking creature

3-10 Creature does not deal combat damage

11-19 Creature deals combat damage

20  Critical hit! Creature gains double-strike until end of turn

For each evasive creature that attacks (flying, trample, skulk, etc. are all treated the same):

1-2 Opponent responds! Destroy target attacking creature

3-6 Creature does not deal combat damage unless it is unblockable (such as Blighted Agent)

7-19 Creature deals combat damage

20 Critical hit! Creature gains double-strike until end of turn


At various points in the game when you cast a spell, roll a D20; number indicates result:

CMC 4 or less: Spell resolves

CMC 5 to 6: 30% chance of counter (1-6 on a D20)

CMC 7+: 50% chance of counter (1-10 on a D20)

For a big attack, rolling a bunch of D20s in a box lid works great.

A Few Caveats

  • The first is that Thunderbowl may need to be modified to fit your playgroup’s style. Maybe your playgroup doesn’t run interaction at all, or maybe they run way more interaction. That’s also why counterspells are optional. If Thunderbowl doesn’t feel like what you normally encounter in a game, try substituting different spells on the D20 for your opponent’s turn, or roll two D20s to crank up the difficulty!
  • Thunderbowl can apply to the majority of decks; however, some decks, such as forced combat, politics, and clones decks, must rely on opponents for their strategy. Thunderbowl might not be the best way to playtest these decks (or might be an extra challenge).
  • The last caveat is that we need a little bit of flexibility. Each situation is different. Set yourself reasonable odds for unplanned situations that come up. For example, for Anowon, the Ruin Thief, assume each card you mill is a 30% chance to hit a creature, so roll one D20 for each damage dealt, and draw a card when you roll a 15 or higher.

For convenience, here’s a link to the Thunderbowl rules on a one-page printer-friendly doc.

If you’re interested in helping develop Thunderbowl, you can join this Thunderbowl Discord server, you can comment below, or you can find me on Twitter @jevin_mtg.

Next article, we return to our regularly scheduled programming. Help me choose which commander to Challenge the Stats for next!

I’ll leave you with some Thunderbowl fan-fiction, from its only fan as of now: me.

The wizard entered the stone chamber. It was a dark, cavernous room with rough-hewn walls. In the center was a jagged black crystal on a wide pedestal. It cast a low light that barely reached the walls, but when the wizard touched the crystal, it burned bright and hot for a moment. With a crack, the room expanded outwards in every direction. The walls and ceiling were suddenly hundreds of feet away from the wizard, now shining with light from the crystal. The crystal burned intensely, and snakes of lightning blazed across its menacing surface that now spanned fifty paces across.

The crystal wasn’t exactly like the others that the wizard had defended themselves against, but it offered enough resistance to be a challenge, to allow the wizard to flex their skills and weave mana in a way that resembled a real battle. If the wizard attacked, the crystal would shudder and generate phantoms to block. If the wizard cast a spell, the crystal would lash out and attempt to counter the magic. And the crystal would sporadically spasm violently, wiping out the wizard’s army or sending a lightning bolt directly into the wizard’s chest.

When the wizard was done, the chamber and the crystal returned to their original size, leaving the wizard bruised, exhausted, and stronger.

Jevin Lortie has been playing magic on and off since Portal. He was terrible at Magic as a kid because he built singleton kitchen table decks. He is a nutrition science grad student, so he always tells people to get a healthy serving of fruits and vegetables – especially ramples and drawnanas.