The Old One's Army is a crossover event in Terraria introduced via the 1.3.4 update in collaboration with Dungeon Defenders II. Unlike standard invasions that trigger automatically or require simple items, this tower-defense style challenge requires specific placement items and strategic arena preparation. You'll face waves of fantasy enemies across multiple tiers, culminating in boss fights that test your crowd-control capabilities and arena design.
If you've ever struggled against the Etherian mana mechanics, or failed to protect the Eternia Crystal from swooping wyverns and ogres, you're not alone. Preparing for this event requires understanding how Tavernkeep progression works, how to position your sentries, and which loadouts neutralize crowd surges before they overwhelm your defenses.
Unlocking the Tavernkeep and the Event
To start the event, you first need to find and rescue the Tavernkeep, a special NPC. He spawns anywhere in the world after you've defeated the Brain of Cthulhu or Eater of Worlds. Once rescued, he moves into available housing and sells the essential items needed to trigger the invasion.
You'll need two primary items from the Tavernkeep:
- Eternia Crystal Stand: A pedestal where the event is initiated. It costs 5 Defender Medals (though the first one is often free or cheap).
- Eternia Crystal: The core object you must protect during the event. It costs 25 copper coins.
Place the Eternia Crystal Stand on a flat, wide surface of at least 60-100 blocks on either side. When you place the Eternia Crystal onto the stand, the event begins immediately, spawning portals on the left and right sides of your arena. If the crystal's health drops to zero, you lose the event and must try again.
Event Tiers and Progression
The Old One's Army scales across three distinct difficulty tiers tied directly to world progression. Each tier introduces tougher enemies, more waves, and better rewards.
Tier 1: Pre-Hardmode
You can trigger this tier as soon as you unlock the Tavernkeep in Pre-Hardmode. It consists of 5 waves.
- Enemies: Etherian Goblins, Etherian Goblin Bombers, Javelin Throwers, and the Dark Mage mini-boss.
- Strategy: Piercing weapons and early-game area-of-effect spells like the Water Bolt or Demon Scythe make short work of the goblin hordes. Position your sentries near the crystal to catch enemies as they close in.
Tier 2: Hardmode (Post-Mechanical Bosses)
Once you defeat any of the three mechanical bosses (The Twins, The Destroyer, or Skeletron Prime), the event upgrades to Tier 2, increasing to 7 waves.
- Enemies: Wither Beasts, Kobolds, Etherian Lightning Bugs, and the Ogre mini-boss.
- Strategy: Ogre enemies deal massive melee damage and launch projectile spit balls. Keep your distance and use high-mobility wings or mount items. Crowd-control weapons like the Daedalus Stormbow or Frost Staff shine here.
Tier 3: Post-Golem
Unlocked after defeating the Golem in the Lihzahrd Jungle Temple, Tier 3 introduces 7 grueling waves with devastating late-game enemies.
- Enemies: Betsy the Dragon, Dark Mages, Ogres, and flying Drakes.
- Strategy: Betsy is the final boss of the event and attacks with sweeping fire breath, dashes, and fireballs. You'll need high-tier armor (Shroomite, Beetle, or Spectre), optimized arenas with heart lanterns, and high-DPS ranged or magic weapons to survive her flight patterns.
Defender Medals and Tavernkeep Rewards
The primary currency earned from completing waves and defeating mini-bosses/bosses is Defender Medals. These medals are dropped upon completing waves, with higher tiers yielding significantly more currency.
You can spend Defender Medals to buy powerful armor sets, unique accessories, and sentry summons from the Tavernkeep. Each class receives a dedicated armor set that boosts specific sentry capacities and mana regeneration:
- Apprentice Set: Tailored for magic users, boosting magic damage and sentry count.
- Squire Set: Built for melee fighters, offering high defense, health regeneration, and melee boosts.
- Huntress Set: Designed for ranged players, providing trap bonuses and ammunition conservation.
- Monk Set: Focuses on melee speed, movement, and agile movement styles.
Designing the Ultimate Arena
Building a dedicated arena is the single most important factor for success, especially in Tiers 2 and 3. Because the Eternia Crystal Stand requires a wide, flat space, avoid putting walls or obstacles that block your movement or projectile paths.
- Flat Runways: Construct a long, flat surface of asphalt or platforms so you can run continuously while kiting fast-moving enemies like Kobolds.
- Sentry Platforms: Build small elevated steps or platforms near the crystal stand to place your sentries. This elevates them above ground-level chaos and expands their targeting lines.
- Honey and Campfires: Place pools of honey, campfires, and heart lanterns near the crystal stand to maximize your health regeneration during intense waves.
- Telegraphing Spawns: Watch the ground where portals appear at the edges of your arena. Clear line-of-sight lets you pre-cast area spells right as enemies step through.
Common Mistakes to Avoid
Many players fail their first attempts at the Old One's Army due to avoidable tactical errors. Keep these pitfalls in mind:
- Ignoring Sentry Synergy: Don't just rely on your primary weapons. Sentry summons like the Flameburst or Lightning Aura deal automatic passive damage that chips away at massive goblin surges.
- Fighting Too Far from the Crystal: If you kite enemies all the way to the edge of the map, you risk missing stragglers that slip past you to attack the crystal directly. Keep the fight centered near the middle.
- Underestimating the Ogre: Getting caught in the Ogre's stomp attack or sticky oil puddles is lethal in Hardmode. Always jump or dash backward when you see the Ogre wind up its heavy attack.
- Wrong Loadout Selection: Single-target weapons will leave you overwhelmed during early waves. Swap to piercing ammunition, whips, magic books, or yoyos with wide hitboxes.
Frequently Asked Questions
Can you trigger the Old One's Army underground?
No, the Eternia Crystal Stand requires a large, flat open space on the surface layer. Placing it underground or in cramped caverns will prevent the event from starting.
Do Defender Medals drop in multiplayer?
Yes, all participating players who deal damage during the event receive Defender Medals when waves are cleared, making multiplayer cooperative play an efficient way to farm currency.
What happens if the Eternia Crystal is destroyed?
The event ends immediately, surviving enemies despawn, and you are awarded Defender Medals only for the waves you successfully completed. You will need another Eternia Crystal to try again.
Are the Tavernkeep items useful against Moon Lord?
Several weapons and accessories bought with Defender Medals—such as the Ballista Panic! accessory or high-tier sentry staves—provide excellent supplementary damage that remains competitive even during late-game encounters like Moon Lord.
