How do I prepare for the Old One's Army event in Terraria?

The Old One's Army is a unique event in Terraria that combines tower defense mechanics with traditional combat. It is triggered by placing an Eternia Crystal Stand and using an Eternia Crystal, which can be purchased from the Tavernkeep NPC. The event consists of waves of enemies that attack the crystal, and your goal is to defend it until the final wave is defeated. Preparing for this event requires careful planning, as it tests both your combat skills and your ability to manage resources and defenses.

First, letÔÇÖs discuss the mechanics of the event. The Old One's Army has three tiers, each corresponding to different stages of the game: pre-Hardmode, early Hardmode, and post-Plantera. The difficulty and rewards increase with each tier. The event takes place in a fixed arena, and you must protect the Eternia Crystal from being destroyed by enemies. You can place sentries, which are special turrets sold by the Tavernkeep, to help defend the crystal. These sentries are crucial for success, as they provide additional firepower and crowd control. The event progresses in waves, with each wave becoming progressively harder. The final wave features a powerful boss, such as Betsy in the post-Plantera tier.

To prepare for the Old One's Army, you need to build a proper arena. The arena should be flat and wide, with enough space to place sentries and maneuver around enemies. Platforms can be used to create multiple levels, allowing you to dodge attacks and position yourself strategically. Place heart lanterns, campfires, and honey pools around the arena to provide health regeneration. Additionally, consider using traps and lava to deal passive damage to enemies. However, be cautious with lava, as it can destroy dropped items.

Next, focus on your equipment and class setup. The Old One's Army is challenging, so youÔÇÖll need strong weapons and armor. For melee players, weapons like the Terra Blade or the Influx Waver are excellent choices. Ranged players should use weapons such as the Tsunami or the Megashark, while magic users can rely on the Razorblade Typhoon or the Nebula Blaze. Summoners should equip powerful minions like the Stardust Dragon or the Xeno Staff. Accessories like the Celestial Shell, Ankh Shield, and Wings are essential for mobility and survivability. DonÔÇÖt forget to use buff potions, such as Ironskin, Regeneration, and Endurance, to boost your stats.

Sentry placement is a key strategy in the Old One's Army. The Tavernkeep sells different types of sentries, each with unique abilities. For example, the Ballista sentry deals high single-target damage, while the Explosive Trap sentry is great for crowd control. Place sentries in strategic locations to cover all approaches to the crystal. Upgrade your sentries by using Defender Medals, which are earned by completing waves of the event. Prioritize upgrading sentries that deal the most damage or have the best area coverage.

During the event, focus on managing your sentries and dealing with high-priority targets. Some enemies, like the Dark Mage or Betsy, can deal massive damage to the crystal if left unchecked. Use your strongest weapons to eliminate these threats quickly. Keep an eye on your health and use healing items like the Nurse NPC or healing potions when necessary. If the crystal is taking too much damage, consider using the Rod of Discord to teleport back to it and defend it directly.

Common mistakes to avoid include neglecting sentry placement, underestimating enemy waves, and failing to upgrade your equipment. Sentries are your primary defense, so always place them in optimal locations. DonÔÇÖt assume that early waves are easy, as they can quickly overwhelm you if youÔÇÖre not prepared. Always upgrade your weapons and armor before attempting higher tiers of the event.

Advanced techniques include using the Nurse NPC for quick healing and setting up a teleporter network to move around the arena efficiently. You can also use the Frost Hydra sentry, which is obtained from the Ice Golem, to deal additional damage. For resource management, farm Defender Medals in lower tiers before attempting higher ones, as this will allow you to purchase better sentries and upgrades.

In summary, preparing for the Old One's Army requires a combination of strong equipment, strategic sentry placement, and careful resource management. Build a well-designed arena, use buff potions, and focus on eliminating high-priority targets. Avoid common mistakes like neglecting sentries or underestimating enemy waves. With proper preparation and execution, you can successfully defend the Eternia Crystal and earn valuable rewards from the event.