How do I design a base that is safe from the Old One's Army in Terraria?

Designing a base that is safe from the Old One's Army in Terraria requires careful planning and understanding of the event's mechanics. The Old One's Army is a wave-based event where you must defend the Eternia Crystal from enemies that spawn from portals on either side of the arena. The event is triggered by placing an Eternia Crystal Stand and using an Eternia Crystal, which can be purchased from the Tavernkeep NPC. To create a base that can withstand this event, you need to focus on defense, strategic placement of structures, and efficient use of resources.

First, let's discuss the mechanics of the Old One's Army. The event consists of multiple waves of enemies, each wave becoming progressively harder. The enemies will spawn from portals on either side of the Eternia Crystal Stand and will attempt to destroy the crystal. If the crystal is destroyed, the event ends in failure. The event can be fought in three tiers, depending on your progression in the game: Tier 1 (pre-Hardmode), Tier 2 (post-Mechanical Bosses), and Tier 3 (post-Golem). Each tier introduces stronger enemies and more challenging waves.

To design a base that can protect the Eternia Crystal, you need to create a fortified arena with multiple layers of defense. Start by choosing a flat area or flattening the terrain where you plan to place the Eternia Crystal Stand. The arena should be at least 60 blocks wide to give you enough space to maneuver and fight the enemies. Place the Eternia Crystal Stand in the center of the arena.

Next, build walls on either side of the arena to funnel the enemies into a specific path. These walls should be at least 10 blocks high to prevent enemies from jumping over them. Use strong blocks like Stone or Bricks to ensure the walls are durable. You can also add a roof to the arena to prevent flying enemies from bypassing your defenses.

Inside the arena, create platforms at different heights to give yourself and your NPCs multiple levels to attack from. Platforms should be spaced about 6-8 blocks apart to allow for easy movement and jumping. Place traps like Dart Traps, Super Dart Traps, and Flame Traps along the walls and platforms to deal damage to enemies as they approach. These traps can be activated with pressure plates or timers.

To further enhance your defense, place sentries like the Ballista, Explosive Trap, and Lightning Aura around the arena. These sentries can be purchased from the Tavernkeep and are essential for dealing with large groups of enemies. Make sure to place them strategically to cover all angles of attack.

NPCs can also play a crucial role in defending your base. Place NPCs like the Nurse, Arms Dealer, and Demolitionist near the arena to provide healing, ammunition, and explosives. The Nurse can heal you during the event, while the Arms Dealer and Demolitionist can supply you with necessary items.

Resource management is key to preparing for the Old One's Army. Gather materials like Stone, Wood, and Iron to build your arena and traps. You will also need a steady supply of coins to purchase sentries and other items from the Tavernkeep. Make sure to stock up on healing potions, ammunition, and buffs like Ironskin and Regeneration to increase your survivability during the event.

Common mistakes to avoid include not having enough traps or sentries, not building high enough walls, and not preparing enough resources. Make sure to test your arena before starting the event to ensure everything is working correctly. You can also practice fighting the Old One's Army in lower tiers to get a feel for the event and improve your strategies.

Advanced techniques include using lava traps, teleporters, and actuators to create more complex defenses. Lava traps can be placed at the bottom of the arena to deal continuous damage to ground enemies. Teleporters can be used to quickly move around the arena and avoid enemy attacks. Actuators can be used to create hidden passages or traps that can be activated during the event.

In terms of class and equipment considerations, the Summoner class is particularly effective in the Old One's Army event due to the ability to summon multiple minions to fight for you. The Stardust Dragon and Terraprisma are powerful summon weapons that can deal significant damage to enemies. For other classes, make sure to use weapons and armor that are appropriate for your current tier. For example, in Tier 1, use weapons like the Minishark or Bee's Knees, and in Tier 3, use weapons like the Terra Blade or Vampire Knives.

In conclusion, designing a base that is safe from the Old One's Army in Terraria requires careful planning, strategic placement of defenses, and efficient use of resources. By following these steps and tips, you can create a base that can withstand the waves of enemies and protect the Eternia Crystal. Remember to test your defenses, gather necessary resources, and choose the right class and equipment to maximize your chances of success.