When playing this game, don't think to yourself 'Crypts are now costing me 240, but Dens only cost 160, I'll get some more dens.' Crypts > Temples > Dens, in most cases a crypt is worth twice as much as a den, especially if you have been using your skills points on them.
 "Insectonator: Zombie mode"){kind=icon}
 "Rebuild"){kind=icon}
 "Cursed Treasure: Don't Touch My Gems!"){kind=icon}
 "Xeno Tactic"){kind=icon}