Events

An event replaces the world's normal spawn rules for a while. Instead of whatever a biome would usually produce, the game feeds you a fixed roster at a much higher rate, and it stops caring that you built a town on that spot. Some events roll their own dice at dawn or dusk. Others only happen because somebody used a summoning item on purpose. Either way the payoff is the same: those rosters carry drops that exist nowhere else, so events are how most of the best gear enters a world.

This is the thing that confuses newcomers most. Goblin, pirate, Frost Legion and Martian invasions are objects with a location on the map. Three of them start at a world border and travel toward the spawn point at sixty tiles per second, which is about 35 seconds on a small world and about 70 on a large one. Enemies appear near that moving location and nowhere else. If you are more than roughly 187 tiles to the side of it, or deeper than about 67 tiles below the surface line, the game spawns nothing at all and the event looks broken.

There is a second way to qualify. Once the invasion has effectively reached the center of the world, standing near any town NPC also counts, and that NPC can be housed as high or as low as you like since only the horizontal gap is checked. The catch is that this route converts only about two thirds of spawns into event enemies, so a farm anchored to a town runs slower than one built at the front line.

Invasions end when you have killed enough of them, and the requirement scales with how many players in the world are carrying 200 or more maximum health when it starts. A goblin or Frost Legion run wants 120 kills solo and another forty per extra qualifying player. Pirates want 180 and sixty per player. Martians want 200, but their saucers are worth ten kills each and their turrets are worth nothing. Dying does not reset any of that, and neither does quitting, because the counter is written into the world file.

The Pumpkin Moon and Frost Moon ignore kills entirely and run on a points score per wave, and both end at 4:30 AM whatever wave you reached. The Blood Moon and Solar Eclipse track nothing: they take the whole night or the whole day and then leave on schedule.

Plenty of this list is not a fight. Rain raises fishing power in every body of water and brings worms to the surface in forests. A starfall night scatters Fallen Stars across the map and spawns Enchanted Nightcrawlers, which is the cheapest bait run in the game. Lantern night follows your first clear of each boss or invasion and hands out a flat luck bonus of 0.3, so that is the night to fish for something rare or open a stack of crates. A party is decoration plus a few NPC-only stock lines and a Party Center can start one whenever you want. Sandstorms and windy days mostly make the surface unpleasant, though sandstorms are the only way to meet several desert enemies.

• Building the arena at spawn and then fighting from a skybridge or a tunnel. Extra height is fine, extra depth is not.
• Assuming an invasion can be waited out offline. It is saved with the world, so logging off only pauses it.
• Running two at once. Only one invasion exists at a time, and a summoning item used while another is active does nothing and is not consumed.
• Forgetting that the non-invasion events stack on top. A blood moon can land partway through a pirate invasion, and a solar eclipse can share a day with a goblin army.

Two events gate content you will actually want. The goblin army has to be cleared once before the Goblin Tinkerer appears bound in the caverns, and he is the only source of reforging and the Tinkerer's Workshop. Clearing a pirate invasion once moves the Pirate in. Everything after that is optional in the sense that the game can be finished without it, but the Pumpkin Moon and Frost Moon hold most of the strongest post-Plantera weapons, and the Martian Saucer holds the best of the post-Golem ones.