Hunters Credo should be renamed: Hunting with some mining and siege at the end.
Played through the hunters quest, quest 9 was 'defeat bat' - now I have mine 3 map tiles through nothingness to reach the underground questgiver to deliver some raw meat and break into a settlement first as they claimed the only cave entrance nearby -or- mine ~8 map tiles toward the questgiver from the next cave nearby -or- build a minehole.
Really, great fun </sarcasm>- should I play this with a new character (that is unable to mine) and not already been brainwashed by the H&H skinner box I would most likely just rage quit at this point.
Make at least sure that questgivers are reachable (this also counts for walls), for underground ones this would mean that the cave they're in has an entrance.