Building and experience. Put in the simplest way possible, the best way to make every boss in Terraria beatable is through building and experience.
Building a boss arena in all the places you need to fight a boss can be a massive hassle. But if you’re having difficulty with a boss, setting up a suitable boss arena is the easiest way to give yourself a better shot. And just straight-up experience with the boss (and the game, in general) can help just as much as any cheap trick or tactic.
Building a Boss Arena
A good arena allows for both vertical and horizontal mobility, usually meaning long rows of wooden platforms with some solid platforms at set intervals. Along these platforms, you can place a number of things that will give you an edge:
And, as a few general things, some nice things to have nearby are aCrystal Ball(for magic users), anAmmo Box(for ranged users), aBewitching Table, and theNurse.
Here’s a video fromZuzucornthat outlines the process of setting up a nice arena (with a little lava trap inclusion, should you like the idea):
Related:How to Summon All Bosses in Terraria
Tips and Tricks
Here are a few useful strategies for making a boss fight a heck of a lot easier:
