How do I build a base that can handle Old One's Army events in Terraria?

Building a base to handle the Old One's Army event in Terraria requires careful planning, as this event involves waves of powerful enemies and bosses that will test your defenses. The Old One's Army is a tower defense-style event where you must protect the Eternia Crystal from being destroyed. To succeed, you need a well-designed arena, proper equipment, and a solid understanding of the event mechanics.

First, let's discuss the mechanics of the Old One's Army event. The event is triggered by placing an Eternia Crystal Stand and an Eternia Crystal in a flat area. Once activated, waves of enemies will spawn from portals on either side of the arena. Your goal is to defend the crystal from these enemies. The event has three tiers, with each tier increasing in difficulty. Tier 1 is accessible pre-hardmode, Tier 2 in early hardmode, and Tier 3 after defeating Plantera. The enemies in each tier are stronger and more numerous, so your base must be adaptable to handle these challenges.

To build a base for the Old One's Army, start by selecting a flat area. The arena should be at least 100 blocks wide to give you enough space to maneuver and set up defenses. Clear out any obstacles and ensure the ground is level. Next, place the Eternia Crystal Stand in the center of the arena. The crystal will be placed on this stand during the event, so make sure it is easily accessible.

Now, let's focus on the arena design. The arena should have multiple layers of platforms to allow for vertical movement. Place at least three layers of platforms, spaced about 10 blocks apart. This will give you room to dodge enemies and attack from different angles. Use solid blocks for the platforms to prevent enemies from passing through. You can also add walls on the sides of the arena to funnel enemies into specific paths, making it easier to target them.

Defense mechanisms are crucial for surviving the Old One's Army. Traps and sentries can be highly effective in this event. Place traps like spear traps, flame traps, and spiky ball traps along the enemy paths. These traps will deal damage to enemies as they approach the crystal. Sentries, which are summoned using sentry weapons, can also help by automatically attacking enemies. Place sentries strategically around the arena to cover all angles.

Lighting and buffs are also important. Place campfires and heart lanterns around the arena to provide health regeneration. Use heart statues wired to timers to spawn additional hearts during the event. Buffs from potions like Ironskin, Regeneration, and Swiftness can significantly improve your survivability. Make sure to have a stock of these potions before starting the event.

Resource management is key to building a successful base. Gather materials like stone, wood, and iron to craft platforms, walls, and traps. You will also need wires and mechanisms to set up traps and heart statues. Plan ahead and gather these resources before starting the event. If you are in hardmode, consider using stronger materials like adamantite or titanium for your platforms and walls.

Class and equipment considerations are also important. The Old One's Army event favors classes that can deal consistent damage from a distance. The Ranger class is particularly effective, as it can attack enemies from afar with bows, guns, and repeaters. The Summoner class can also be useful, as sentries and minions can help defend the crystal. Make sure to equip the best armor and weapons available for your class. Accessories that increase damage, defense, and mobility, such as the Ranger Emblem, Ankh Shield, and Lightning Boots, are highly recommended.

Common mistakes to avoid include not having enough space in the arena, neglecting to set up traps and sentries, and not using buffs. Make sure your arena is wide enough to handle the waves of enemies. Traps and sentries are essential for dealing with large groups of enemies, so don't overlook them. Buffs can make a significant difference in your survivability, so always use them before starting the event.

Advanced techniques include using lava traps and teleporters. Lava traps can be placed in narrow paths to deal continuous damage to enemies. Teleporters can be used to quickly move around the arena, allowing you to respond to threats more efficiently. These techniques require more resources and planning but can greatly enhance your defenses.

In summary, building a base to handle the Old One's Army event in Terraria requires careful planning and preparation. Design a wide, multi-layered arena with platforms, walls, and traps. Use sentries and buffs to enhance your defenses. Gather the necessary resources and equip the best gear for your class. Avoid common mistakes and consider advanced techniques like lava traps and teleporters. With the right setup, you can successfully defend the Eternia Crystal and emerge victorious in the Old One's Army event.