Your first boss fight

Learn how to prepare for and defeat your first Terraria bosses, King Slime and Eye of Cthulhu. Includes crafting, arena building, and strategy tips.

Now it's time for your first boss fight. Go back to your home and create a Furnace from torches & stone blocks and then place it. Then create an Anvil from Iron or Lead ore and then place it near (or wherever) your Furnace. This will be your basic blacksmithing station, a station you will be using a lot. Feel free to also place a workbench near it as well to create a sort of all-in-one crafting station. Other crafting stations exist, but you use the Furnace/Anvil/Workbench the most often in the game.

Craft Iron/Lead armor & weapons. This should be a bow and arrows. If you have spare ore, you can create an Iron/Lead sword. Not a shortsword. A normal one. Shortswords are fine, but they're very short range. Normal swords swing in an overhead fashion and are much easier to use with better range.

You will also want a grappling hook. Grappling hooks are a powerful equipment item with their own special slot. They allow the player to shoot a hook from their body that will connect to a surface and then keep them there. You can then grapple again while attached to connect yourself somewhere else. They provide powerful maneuverability and are very important in pre-hardmode, and even get used in hardmode for a while.

Building your arena

In order to properly fight bosses, you need to construct an arena. An arena is simply a structure built in order to help you win the boss fights in Terraria. What your arena looks like can (and will) change based on the different bosses you fight. At the absolute basic, it'll be lines of wooden platforms that have ropes on the end. It should be the width of your screen, or a bit longer than that if you're on a smaller resolution like 1366x768 (like I am).

This is a basic arena setup for daytime. However, for night time, you're going to want torches placed throughout so you have night time vision while fighting the boss. It'll look like this:

Notice I've added campfires. Campfires are a basic addition to any boss arena, daytime or night time. They provide a small boost in HP regeneration within a certain tile radius of them. They should always be on all day & night arenas. There are other additions you can make to these arenas. Such as adding blocks and placing Heart Lanterns under them (crafted from chains and life crystals) which provide a stronger boost than campfires. They stack with campfires, however, you need precious life crystals to craft them. So hold off on placing one or two in your arena(s) until around 300 HP. You can also add small U shaped sections made from whatever blocks you wish with honey in them. That's a liquid found in the Jungle biome that applies a 30 second HP regen buff the instant you touch said liquid.

There's a bunch of other modifications you can make to your arena(s) that are useful, but are too much for this section. Instead, visit my arena construction section to see more about that.

Which boss will I be fighting?

Your first boss can be one of two bosses. It will be either King Slime or Eye of Cthulhu. King Slime is considerably weaker and easier than Eye of Cthulhu, but you likely won't see it as your first boss because of its natural spawn conditions. Eye of Cthulhu spawns much easier naturally. That being said, I will be tackling both bosses in this section.

Before you take them on, however, you should acquire a couple of movement accessories. Accessories come in categories. Movement ones will, obviously, help you move in various ways better. You'll want to search underground for chests to try to find Hermes Boots. They'll greatly increase your movement speed. You can also find Sailfish boots (Wooden and Iron Crates from fishing) and Flurry Boots (Ice biome chests). They're all functionally the same. You'll also want to try to get Cloud in a Bottle from underground chests. Maybe even Blizzard in a Bottle from Ice chests. They provide you with double jump functionality.

King Slime Boss

• Natural spawn conditions: Trigger a Slime Rain event by having 140+ HP and 8+ defense. Each starting day has a 5% chance to trigger this event in pre-hardmode. 3.3% in hardmode. Kill 150 slimes (75 if you've killed King Slime at least once). Once you do, King Slime will spawn.
• Summoning item: Craft a Slime Crown. This can be done by making a Gold/Platinum Crown from x1 Ruby and x5 Gold/Platinum bars. Then take it and x20 Gel to a Corrupted or Demon Altar and craft it. Those altars are located in your evil biome, scattered throughout.

Additional natural spawning note: It is possible for King Slime to spawn in the outer edges (near the Ocean) of your world if there is grass. This will almost _never_ happen naturally because of how far worldgen places the Forest biome from the Ocean/sandy bits. So if you do want this to happen, 99.99% of the time, you will need to create an area with dirt blocks and grass will naturally grow on them (you can plant grass seeds as well, bought from the Dryad NPC). Then he can rarely spawn there.

King Slime basically has no attacks to speak of. It deals damage by coming into contact with you. It will do short range arcing jumps towards you, which will deal some damage if it touches you. It can also teleport very so often. The tell for this is when it starts shrinking its body. When it does, move from where you are as quickly as possible, ideally using the grappling hook to quickly get out of the way. It attempts to teleport on top of your character model.

Other than that, nothing special. Dealing damage to the King Slime causes it to birth slimes from its body that you'll need to deal with at your discretion.

Expert mode note: in expert mode, King Slime will dislodge Spiked Slimes from its body. These deal more damage than the normal slimes do and have a ranged attack that you'll need to avoid. Take them out as soon as possible and keep your distance the best you can.