There are 28 gems available for sell but this number may be changed in merchant_gems2.dat file. Just change <INTEGER>MIN and <INTEGER>MAX values in TREASURE group.
I've tried to increase prices for this merchant, but haven't found the way to do it (I've played with PRICE REDUCTION effect and negative values but it doesn't seem to work). I'll be glad if someone finds out if this is possible and how to do it.
DOWNLOAD HERE: http://www.runicgamesfansite.com/torchlightmods/node/184
OR HERE: http://torchlit.net/latest-mods/item/72-gem-merchant.html
Anya's Gems Emporium




