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

The Old One's Army is a unique wave-based event in Terraria that requires careful preparation and strategy to succeed. This event is tied to the Tavernkeep NPC, who sells special items and armor sets designed for this event. The event has three tiers, each corresponding to different stages of the game: Tier 1 (pre-Hardmode), Tier 2 (early Hardmode), and Tier 3 (post-Plantera). To prepare for the Old One's Army, you need to focus on several key aspects, including understanding the event mechanics, building a proper arena, selecting the right gear, and managing resources effectively.

First, let's discuss the mechanics of the Old One's Army. The event revolves around defending the Eternia Crystal, which is placed on a special stand called the Eternia Crystal Stand. Waves of enemies will spawn from portals on either side of the map and attempt to destroy the crystal. If the crystal is destroyed, the event ends in failure. You must survive multiple waves, with each wave becoming progressively harder. The final wave includes a powerful boss, such as the Dark Mage in Tier 1, the Ogre in Tier 2, and Betsy in Tier 3. Successfully completing the event rewards you with Defender Medals, which can be used to purchase powerful items from the Tavernkeep.

To prepare for the event, start by building an arena. The arena should be a flat, open space with enough room to maneuver and fight enemies. Place the Eternia Crystal Stand in the center of the arena. You can use platforms to create multiple levels, allowing you to attack enemies from above or below. Traps, such as dart traps and flame traps, can be placed around the arena to deal additional damage to enemies. Lava pits can also be effective, but be careful not to place them too close to the crystal, as they can damage it. Additionally, consider adding heart statues and star statues connected to timers to provide healing and mana regeneration during the event.

Next, focus on your gear and equipment. The Old One's Army event is unique in that it has its own class system, known as the Sentinel class. The Tavernkeep sells Sentry Summon weapons, which are essential for this event. These weapons summon stationary turrets that automatically attack enemies. For Tier 1, the Ballista Rod is a good choice, while Tier 2 and Tier 3 offer more powerful options like the Explosive Trap Rod and Lightning Aura Rod. Pair these with armor sets like the Apprentice, Squire, or Monk sets, which are also sold by the Tavernkeep and provide bonuses to Sentry damage and summon capacity.

In addition to Sentry weapons, you should also equip a primary weapon for direct combat. Melee weapons like the Night's Edge or the Terra Blade are effective for close-range combat, while ranged weapons like the Megashark or the Daedalus Stormbow can deal consistent damage from a distance. Magic users can rely on weapons like the Crystal Serpent or the Golden Shower, and summoners can use minions like the Spider Staff or the Optic Staff to assist in combat. Accessories like the Warrior Emblem, Ranger Emblem, or Sorcerer Emblem can boost your damage output, while the Celestial Shell or Ankh Shield provide additional survivability.

Buff potions are crucial for surviving the Old One's Army. Potions like Ironskin, Regeneration, and Swiftness provide essential stat boosts, while Endurance and Lifeforce potions increase your survivability. Magic users should stock up on Mana Regeneration and Magic Power potions, while summoners can benefit from Summoning potions to increase their minion count. Food items like Cooked Fish or Pumpkin Pie provide the Well Fed buff, which boosts all stats.

One common mistake players make is underestimating the importance of Sentry weapons. While your primary weapon is important, Sentry weapons are the backbone of your defense in the Old One's Army. Make sure to place your Sentries strategically, focusing on areas where enemies are likely to gather. Another mistake is neglecting to build a proper arena. A poorly designed arena can make it difficult to defend the crystal, leading to failure. Take the time to create a well-thought-out arena with traps, platforms, and healing stations.

Advanced techniques include using the Nurse NPC to heal during the event. Place a house for the Nurse near your arena so you can quickly heal when your health is low. Additionally, consider using the Dryad NPC to provide the Dryad's Blessing buff, which increases your defense and reduces enemy damage. For Tier 3, the Betsy boss can be particularly challenging. Focus on dodging her attacks and use high-damage weapons like the Solar Eruption or the Phantasm to take her down quickly.

In summary, preparing for the Old One's Army requires a combination of strategic arena building, proper gear selection, and effective resource management. Focus on Sentry weapons, build a well-designed arena, and use buff potions to enhance your combat effectiveness. Avoid common mistakes like neglecting Sentry weapons or building a poor arena, and consider advanced techniques like using the Nurse or Dryad for additional support. With the right preparation, you can successfully defend the Eternia Crystal and earn valuable Defender Medals to purchase powerful items from the Tavernkeep.