Every night time stars fall from the sky. Collecting ten of these increases your maximum mana. On normal terrain this can take a long time and can be a risky in pitch-darkness. By creating a Sky Bridge (by making a ladder around a hundred or so blocks in the air and laying down stone or dirt in a straight line), you can create a long stretch of land for the stars to land on. With a speed-increasing item such as Hermes Boots or Necro Armor equipped, you can travel the length of your bridge while collecting stars very easily. Zombies will still spawn on the bridge and you might get the occasional harpy or demon eye, but you won't have to deal with rough terrain, chasms, water or anything that spawns from the corruption.