When you kill a kobold or werewolf in Errac Tierra Dias or Tierra Noche, there is a 1% chance that you can (quite literally) beat the shit out of them. This Excrement Lump (aka Night Soil in GE-SG) can be used at the farm in Errac (I3/J3) to receive 1 Gold Corn. You can then exchange 10 Gold Corns for a random reward from Vagabond Peddler in New Opoluto (E3). The known rewards are:
I have exchanged a fair amount of corns, and these are the rewards I received so far. This post will be updated if I find more possible rewards.