The Old One's Army is a tower defense-style event that contains cross-over content from the game "Dungeon Defenders 2". This unique event has many elements from the DD2 game that includes enemies, bosses and items. The music played during the event is also a reference to the tower defense game.



  • The Tavernkeep NPC must first be found in the world. Once discovered, the Eternia Crystal and Eternia Crystal Stand can be purchased to initiate the event.
  • The crystal stand must be placed on a long, flat surface or the crystal will fail to be placed there and a status message will be given for the criteria needed.
  • Only one stand is needed, as it does not consume with each summoning. However, the crystal that is placed inside does consume with each event triggered.

Game Progression

To start the event, an Eternia Crystal must be in the player's inventory and they can place it into an Eternia Crystal Stand by right clicking on it. If the land is suitable, two Mysterious Portals will appear approximately 130 blocks away from each side of the stand, and the Old One's Army will approach after 5 seconds. The player must then fend off several waves of enemies until the event ends to claim victory. Apart from defending the crystal with towers and having multiple waves, it is similar to other invasion type events such as the Goblin Army. This event has 3 distinct tiers of difficulty, depending on when the player attempts to trigger it:

Pre-Mechanical Boss

Post-Mechanical Boss and Hardmode

Post-Golem and Hardmode

  • Consists of 7 waves.
  • 100 total Defender Medals earned.
  • Contains all of the enemies from tier 1 and 2, as well as Etherian Lightning Bug, and Betsy (final boss).

The event ends when either the player wins by defeating the final wave of the current tier or loses when the Eternia Crystal is destroyed.


  • When the event is started, the player receives the creative shock debuff and building of any kind isn't possible until the event ends. Any arena prep should therefore occur before placing the crystal as long as it does NOT affect the surface. 
  • Any pre-placed sentry-style enemies in the arena despawns when the event starts but the ones that does not consume Etherian Mana can be used freely after. 
  • Upon placing the crystal into the stand, the player receives 10 free Etherian Mana, which is needed for each cast of a sentry. More mana can be gathered from enemies killed.
  • When talking to the Tavernkeep, selecting "Eternia Crystal" for the first time will grant 5 free Defender Medals; just enough to buy one sentry. He will also explain the event.
  • In between each wave, there is "downtime" of 30 seconds and the countdown to zero will be displayed over the crystal, during which enemies do not spawn until the count is over. This is a good time to collect Etherian Mana, Hearts, and Stars.
  • Most enemies scale in health, damage, and appearance when the next tier is reached. The Eternia Crystal itself will also scale in health, having 1000, 3000, and 5000 health for each of the 3 tiers respectively.
  • Banners will drop from all normal enemies, although they will not give buffs against their respective enemy. Some also require more than average kills for the drop, such as Etherian Goblin requiring 1000 for each banner.
  • In tiers 1 and 2, Dark Mages and Ogres can be killed multiple times over the course of the final wave, respawning every time they die. However, Betsy can only be killed once and the event will end when she is defeated.
  • Event Enemies are not affected by Lava and Teleporters.
  • Creative Shock debuff does not affect Dirt Rod's ability to move Dirt, Sandgun's ability to shoot Sand, or Ice Rod's ability to place down temporary Ice Blocks. It also does not prevent Explosives from being used, therefore it can still destroy blocks.
  • If solid blocks block the enemies, they will phrase through them as if the blocks are not present.
  • Actuators remain useful as they can transform the arena throughout the battle. The player can make a wall that prevents some of the projectiles from passing through (protecting the crystal), and use actuators whenever they need to get through the wall.
  • Conveyor Belts can be used to move items to the player, and they can't move enemies. This makes picking up Etherian Mana and the enemies' other drops easier.
  • While traps can be used, they are significantly less useful because they deal low damage.


  • In general, it is best to lay down the Eternia Crystal Stand on a flat surface and give a good amount of room on either end so that there is more time to deal damage to the oncoming enemies.
  • Use the downtime wisely to rebuff, re-cast sentries, and gather any Etherian Mana left to place more ground sentries.
  • If you are trying to complete the Pre-Mechanical Boss (and maybe even the Post-Mechanical), then a good strategy is to use the Demon Scythe about 5 times each way, since it can blast through the weaker enemies like a Flail.
    • Another item for the Pre-Mechanical Boss/Post-Mechanical Boss is the Blessed Apple, which will summon a Unicorn Mount. Not only can it speed up to very high speeds, if it runs into enemies, it can cause about 40 damage.
      • The Unicorn Mount, along with its damage, can run over a whole wave. Keep in mind that the enemies should be smaller ones, like the Etherian Goblin, Etherian Goblin Bomber, etc.
  • When in Pre-Hardmode, buy the Lightning Aura Rod first and start the event. First, put 1 aura near a portal, so when the enemies spawn they'll instantly start taking damage. Keep placing more and more of these, each one a bit closer to the Crystal. It is advised you have 1 Space Gun and a full set of Meteorite Armor to get the Set Bonus.
  • Additional Lightning Aura sentries on either side of the crystal will deal with the groundings by themselves allowing the player to focus on the air borne troops. Placing Flameburst sentries will assist with this.
    Capture 2017-10-05 18 34 38

Update Info


  • Bug fixes.


  • Added to the game.
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