I've upgraded the Cathedral to level 15, but I'm stuck from level 16.

I'm trying to reach hidden level 18. I'm stuck at level 14 because I'm short on materials. When you're not playing, send your farm to gather resources and then log off. Join a guild, send out both your gatherers, and log off!!!! If there are level 6 or 7 gather spots nearby, go for them (but you need a lot of soldiers to gather from higher level spots). I played Whiteout Survival hard for years, but quit about half a year ago... It's exactly the same. The bear is cheese. I'm a total beginner, but I found myself playing like a veteran... ㅡㅡ? So I played it more easily and had fun. I need to hit level 18 quickly before I get too hooked ㅠㅠ