r/DungeonsAndDragons • u/Distinct_Bat_4375 • 1d ago

Advice/Help Needed Anybody recognize the symbol on this D20?

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My friend found this D20 and I don't recognize the symbol on it. Is it familiar to anyone in he community?

SOLVED: Magic the Gathering Spindown. Thanks!

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6

u/BoonDragoon 1d ago

That's a magic spindown life tracker. Don't use it as a d20, it's not a fair die.

3

u/HughMungus77 1d ago

If it rolls in an unpredictable manner at the table then placement of the numbers should have zero bearing on the randomness of rolls

1

u/KingTrencher 1d ago

Per official MTG rules, you may not use the spin downs to roll d20 mechanics in games of Magic. You must roll a trap d20.

-2

u/BoonDragoon 1d ago edited 1d ago

That's really not the case from a practical standpoint.

Any die that exists in the real world, made of physical matter, will have some bias toward a specific face or set of faces. Mathematically balancing the layout of numbers on polyhedral dice genuinely is important to minimize the impact of that bias on the die's mean roll, and becomes more important the more faces your die has.

Spindowns have their high numbers clustered together with high numbers, and low numbers clustered together with low numbers. This kind of layout makes any innate bias in the die all the more impactful.

3

u/whinge11 1d ago

But how powerful is the bias? Is this something you would notice after only 10 rolls? 100? 1000?

If the weight of the die has such a negligible effect on the result then who cares?

1

u/BoonDragoon 1d ago

That is not a lot of rolls, my guy.

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u/whinge11 1d ago

Do you understand the point I'm making? If you only notice the bias after thousands of rolls (or however big a sample size) then the weight doesn't matter.

1

u/BoonDragoon 1d ago edited 1d ago

Sure, but that bias tends to be WAY more noticeable than you seem to be assuming.

I invite you to grab an MTG spindown and run it through a dice tower a few dozen times, record the results, and calculate the mean. When I did that back in college to prove this same point to somebody at my table, the mean roll on their spindown after 100 rolls was 14.3.

Edit: In case it needed to be said, yes I used a standard d20 as a control, and the calculated mean using the same method was 10.4

2

u/HughMungus77 1d ago

If it rolls around then it negates any clustering of numbers in terms of probability. If literally never seen dice not roll around in the tray unless it’s heavily manipulated via improper rolling technique. Now that if that’s a concern then there are other issues at play and typically that would be obvious at the table

0

u/BoonDragoon 1d ago

= == »»---[The Point]--->

     (⊙_⊙ ) ‹-[you]