I remember you can buy coal I saw it somewhere I just can't remember the location where it was being sold :'( I'll have to search I think coz mining is lot more time consuming
GUYS JUST USE THE RIDDLE KEY WHILE STANDING IN THE DUNGEON!! I FOUND IT SOMEWHERE I DON'T REMEMBER (NOT IN THIS DUNGEON OBVIOUSLY!! USING IT WILL MAKE ALL THE SPIKES DISAPPEAR!!!! :D
Go to the Calbridge stronghold and talk to the general and u will get a quest follow the steps and you'll get a new farm stuff seller in the end who will sell you hay