Every area on the map gets more dangerous at night. Start exploring at the crack of dawn, and return to base at night. Day time doesn't matter in a dungeon, so they're nice places to relax at night.

Explore Black forest dungeons for red cubes, use them to build portals. Be VERY aggressive with portal use, generally use them any time you land a ship or find a good landmark. Red cubes can be tough to collect, keep an eye out and set up shop next to fire pillars in the swamp.