palimer6

So from what I can tell, this seems to be undocumented. I was messing around with a Pt rom in DSPRE and noticed two hidden items that don't correspond to the same location that share the same activated script. In Wayward Cave, spawnable 2 (behind the hiker double battle) activates script 8008. On Route 207, spawnable 1 (on the ledge that you can only reach through Mt. Coronet, on the wall directly east of the rock climb wall) also activates script 8008. I checked both items out. They are both Red Shards. If you get either one of them before the other, the other one disappears. I also went and checked a DP rom and the same spawnables appear there as well. I didn't have the time to double check in the game, but the red shard should correspond to a Super Potion judging from Bulbapedia's item list of Wayward Cave. It's not a game changing discovery by any means, but I found it nifty nonetheless and couldn't find anything online talking about it. Closest I found was that some sites list the red shard on Route 207 while others don't.

Funnily enough I also just so happened to look into the Great Marsh very recently and your old post helped a lot with the old save editor and its info. Basically the only thing you're missing with your observations on what bytes get changed is that a pokemon appearing in a specific area does not change the whole byte, but only 5 bits of it. Read as little endian 80 ae 36 b7 becomes b7 36 ae 80 or in binary 1011 0111 0011 0110 1010 1110 1000 0000. If we now split that into units of 5 bits we get 10 11011 10011 01101 01011 10100 00000 or 2 1B 13 0D 0B 14 00. The 2 shouldn't be used for Great Marsh calculation here. These values line up with the pokemon you had in your areas if we assign the 5 bit blocks "in reverse". 1B is area 6, 13 is area 5, 0D is area 4, 0B is area 3, 14 is area 2, 00 is area 1. The following table shows which Pokemon each 5 bit block corresponds to in both DP and Pt once you have the national dex. Hex Bin Dec DP Pt 00 00000 0 Croagunk Toxicroak 01 00001 1 Skorupi Kecleon 02 00010 2 Carnivine Kecleon 03 00011 3 Croagunk Carnivine 04 00100 4 Skorupi Skorupi 05 00101 5 Carnivine Croagunk 06 00110 6 Golduck Quagsire 07 00111 7 Croagunk Drapion 08 01000 8 Skorupi Skorupi 09 01001 9 Carnivine Croagunk 0A 01010 10 Roselia Quagsire 0B 01011 11 Staravia Kangaskhan 0C 01100 12 Toxicroak Paras 0D 01101 13 Drapion Drapion 0E 01110 14 Exeggcute Exeggcute 0F 01111 15 Golduck Exeggcute 10 10000 16 Staravia Skorupi 11 10001 17 Croagunk Croagunk 12 10010 18 Skorupi Skorupi 13 10011 19 Carnivine Carnivine 14 10100 20 Yanma Yanma 15 10101 21 Shroomish Shroomish 16 10110 22 Paras Paras 17 10111 23 Kangaskhan Kangaskhan 18 11000 24 Gulpin Gulpin 19 11001 25 Roselia Tropius 1A 11010 26 Staravia Gulpin 1B 11011 27 Croagunk Shroomish 1C 11100 28 Skorupi Skorupi 1D 11101 29 Carnivine Carnivine 1E 11110 30 Roselia Croagunk 1F 11111 31 Golduck Tangela I know that in Platinum, every Pokemon that isn't in the Sinnoh Dex gets replaced with Wooper before you get the National Dex. I don't know how it works with DP, as I was playing Platinum while looking into this. I also went and tried this with manual hex editing of my save file (and fixing the checksum with PKHeX) and changing the area encounters worked like a charm.