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
Haunting is unlocked by beating the game, and apparently is MP only. Glaring, however, is NOT MP only, based on what people have told me about their no-MP talisman farming.
You can't complete the compass if you don't have the magician's pouch bytheway.
Since C2 is only included in that...
And indeed, haunting is MP only - though not given by beating the game, you get it a bit earlier.
I ended up being level 145 or so when i beat the game without the pouch - now that i've done that, i dont really see any need to get the pouch anymore. :P
I've done all of the achievements but five of them, and those five don't seem to work. The achievements in question are the ones for fields G4, Q2, R4, T5, and W1, which ask you to complete the field using only one type of gem. But they don't work. In fact, even before creating the first gem the achievement is "locked." Any fix for this?
@biffspiker I've gotten most of those achievements just fine.
You can't get any of those until after you complete the entire field without having any other gems than the specified type - you get them at the very end of the level. How is the achievement "locked" before creating the first gem? I don't know anything in the game that tells you an achievement is "locked".
If you open up the list of achievements while playing the field, the game indicates that certain achievements are unattainable by putting a red padlock icon over them. A green, opened lock appears on achievements that you already completed. I'm saying these fields start with the red locks.
I have no idea why you are seeing those as locked before you create any gems. I just checked that for myself, and none of those fields give me a locked achievement at the start of the level. And that is still the case for me even though the only ones I have left are actually unattainable. (I can't get the gems required for those fields because I can't get the magician's pouch)
The only things I can ask/suggest are: -Are you sure you are on the right field? I noticed that field-specific achievements are locked for all other fields, like "oops I'm on F2 when I meant to be on F1" -make sure not to even create gems for bombs or open drop boxes. Even the wrong gem attained from any source or used as a gem bomb etc will negate the achievement.
@Erile
This is actually a bug, it has happened to me to and someone posted about it in the bug reporter, it does actually lock it before you have a chance to earn it @biffspiker
One way around this is to quickly create the required gem before the orb animation completes, for some reason if you wait until after it locks the achievement, but not if you do it before.
I leave K2 and I lost X6 forever! Please tell them to fix this bug!!! tks!(E3 is already tier 5.so I went to play K2,and then I accidendly build my tower at a wrong place,so I leaved it.)same problem as many people
How do I unlock Y1? I already did T6 and unlocked the general Y tile, but usually when you unlocked a hextile you get the first area as well. For example I know K4 unlocks L&O tiles and gives you o1 and L1 to get started.
