added a second purpose to spiral caverns

can now become 'spiral executioner', which gives huge morale boosts for
killing the innocent. tweaks probably needed, because i can't compile atm.

note: i think i added this to my master branch, but i'm not 100% how or why because git is unfamiliar to me. i read the guideline and that would prevent this from being considered/merged, just appreciate some help there

happy thanksgiving