Wow, how did you get bronze on day 20? I was still just hunting/building at that time.

As >< V >< above says. I will just add. That trolls don't start until after you kill Elder. My first troll raids only had 2 trolls. Then I had 3. Not sure how many I get now as my base is big enough with trees outside everywhere that I may not see them all. Or they just may be in the woods meandering. I believe the more trolls you kill, the more trolls you get during the raid.

Best defense is a moat or to raise a stone wall all around. Moat should be 4 to 5 picks deep. You don't want to be swimming in it really. I found just 4 meters wide was good enough. They get stuck if they step in it.

Any structures you don't want hit should be 8 meters away from outside of moat. 10 meters would be better. Cause trolls with a log can reach 8 meters. Make a path with flooring across moat to cross. Leave about a 2 meter or more gap to jump across, cause mobs can't navigate over gaps.

Most general raids (excluding you are being hunted and 1 other) only occur at a base. You have to have 3 things in the area for it to qualify as a base. These include campfire, benches, portals and a bed. so i campfire and 2 benches qualifies. Or 3 benches. or 1 fire, 1 bench, 1 portal.. etc.....