I thought I had seen it somewhere! I looked through the build guide but forgot to check the adventure. Interestingly I feel they've played a little loose with some of the symbols. Like I'm not sure why the triquetra is used to represent treasure. I find their choices for the 3 moons and Horned God interesting as well.They published the Rune symbols. However, like most things, they decided to bury it within the Dungeon of Doom Adventure and not set it out separately for those that only wanted the symbol key.
So I'm going to keep on with this in case others find it useful. Hopefully someone does!
We Start with Elemental symbols here.
C1 🜃 Earth
C2 🜁 Air
C3 🜄 Water
C4 🜂 Fire
C5 ☉ Sun (also Gold)
C6 Sun Rise
C7 Sun Set
C1 ☽ Luna/Moon (also Silver)
C2 Moon Rise - n.b. most representations I've found have the line under the crescent, not above.
C3 Moon Set
C4 & C5 These are Triple Moon symbols, representing the Waxing, Full, and Waning phases of the moon. I do not think there is a difference in the outlined vs. filled in symbol.
C6 & C7 These symbols are the Horned God. Again, I don't think there's a difference between the two.
The Horned God and Triple Moon symbols are used in modern Wicca. While they may be related to older symbols, it can be difficult researching that relation. I've seen quite a bit of incorrect information while trying to do so. (Such as confusing ancient Egyptian deities with Greek.)
C2 ◡ - Dwarven Forge label this as Widdershins, which means counterclockwise. I've not been able to confirm this with the little searching I've done. I think it may be a DF original? The Widdershins symbols I did find had an indication of direction.
More alphabet. Note that X is not present in the alphabet order. You'll find it below in the Roman Numerals and on page 8-02 as mentioned.
Rows 6 - 9, Cols 1 - 3 contain Roman Numerals. If you're not familiar with them they translate to regular (Arabic) numbers as follows:
I = 1
II = 2
III = 3
IV = 4
V = 5
VI = 6
VII = 7
VIII = 8
IX = 9
X = 10
XI = 11
XII = 12
Our circle this time has a Heptagram or Septagram - a Seven-Pointed star.