Reposting this from /r/Gemcraft. These are a collection of the discovered secrets in Gemcraft: Chasing Shadows. Some of this may be slightly inaccurate, but hopefully compiling all the knowledge here will get us closer to the final answer.
Grey Trees
ReaperGuy on the AG forums figured out GreyTrees, and Seberoth also identified some extra codes. It was discovered that the outside corner squares of the map (zoom out to make them easier to see) are clickable. Various codes inputted will do changes to the game, but so far it's only cosmetic aside from the almost-useless Gift Gems.
The codes are entered with the following scheme (as if they're four corners of a number pad): Southwest = 1 Southeast = 3 Northwest = 7 Northeast = 9
The codes discovered so far are: 11331791 - Grey Trees - To get the achievement, finish any field with this set. 11319773 - Black Orb 13371337 - Spinning tower shots 11379197 - Mossy towers 97713791 - Mossy amplifiers 77919713 - Heavy rain 79797919 - Heavy snow 77311973 - Gift gems 11799397 - Dark monsters 11111111 or any 8 digits of the same number - Mods reset
Assuming up to 8 digits in any given code, there are still over 65k codes to try. I don't think brute forcing these will work. Again, all credit for this discovery goes to ReaperGuy and Seberoth on the AG forums.
Compass
The basic gist is that you need to set all compass pieces to tier 5 and beat the final one that drops the field marker. Rinse and repeat 11 times for talismans and field markers. The third reward is a bugged field marker that prevents the round from finishing. Just manually end it and start on the next compass set. You'll know you have completed them all when the gems no longer show up in the loading screen.
The compasses themselves correspond to the gem tiers you see on the loading screen of compass levels. Teardrop is tier 1, triangle is tier 2, square is tier 3, a "U" shape is tier 4, and an "X" shape is tier 5. Every time the compass tiers reset, the compass correspondences are set to a random orientation, which always follows a pattern of 1-2-3-4-5-4-3-2.
Let me be perfectly clear: The directions on the compass don't matter for any tutorial/description, because where Tier 5 is pointing is random each time you do things such as reload the game, change your skills, or beat a level.
The compass levels, in left-to-right order, are C2, E3, J2, K2, O3, U4, and X7. The easiest level to finish at is E3, with only 24 waves at untraited Looming.
Here is my basic algorithm for setting a compass based upon the gem at the loading screen: Tier 1 - Turn 4 times. Done. Tier 2 - Turn 3 times. Recheck. Tier 3 - Turn 2 times. Recheck. Tier 4 - Turn 7 times. Recheck. Tier 5 - Done (duh).
With this algorithm, tier 2 and 4 always become a tier 3 or 5. Tier 3 always becomes a tier 1 or 5.
The rewards for completion of a certain amount of cycles is as follows: 1 - Field D6 3 - Bugged Field Marker (perhaps supposed to be N7?) 5 - Field O4 (Already acquired through normal progression) 7 - Field P6 9 - Field Q7 11 - Field X6 2, 4, 6, 8, 10th times: Talisman fragments of ascending quality
Missing Fields
This list is FAR from complete or entirely accurate. These are just the notes I have from field markers I have acquired or seen from other sources.
A6 - Complete A4 on Glaring B6 - Complete the achievement "Still Alive B1" D6, P6, Q7, X6 - See compass explanaition above. Y4 (->Y5->Y6) - Complete all waves on X5 without charging up the gem. G4 - Complete the rest of Hex G on Haunted difficulty L5 - Complete L1, L2, and maybe L4 on Haunted difficulty
ok i understood compass enigma. thanks for comments and explanations. very long quest and really very boring. so unfunny !? what was the aim ? this is the shadow on this almost perfect game ... compass
According to the posts, you have to finish the level when the gem displays at grade 5. If you can't finish the level I doubt there is a way to get the reward.
...when I get to X, I'm backing up my game in triplicate so I can expiriment with "beating x5 in different ways" so that I can clear up the mystery of the X5->y4 interactions.
With Compass Quest i got until now : field N7 and P6 Unlocked talisman lvl: 34-42-58-65 ( got them in growing order maybe farming it you get a lvl 100 )
done Compass multiple times: got also Q7 and X6 field unlocked and another talisman lvl 73 then the loading screen in compass fields disappeared. No more compass reward doable.
As previously stated in this thread, you get B6 by completing B1 on Glaring. It has nothing to do with the achievement for field B1. I just confirmed this myself 10 minutes ago. I completed B1 on looming multiple times and nothing, I completed B1 on Glaring and received B6 as the reward.