In order to progress through the game, you will need to understand how to spawn bosses and also know which bosses can help you progress through the game. Many of these bosses hold the materials to progress your character to be faster, to deal more damage, and take more damage. Make sure that you keep up to date with your boss progression or you could make the game much harder on yourself than you intend!
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Many bosses are summoned through the use of summonable items or by breaking a special block. Understanding that these items and blocks are used for more than just decoration can help you conquer the world of Terraria!