Guide:Old One's Army strategies

The Old One's Army invasion event differs from others in that the invading enemies do not attempt to kill the player, instead they focus on destroying the Eternia Crystal used to summon it.

The invasion is separated into three Tiers depending on progression. It will start at Tier 1, and after a Mechanical Boss has been defeated Tier 2 can be fought. Then, after taking down Golem for the first time, Tier 3 is available.

In order to summon the event, the Player must place the Eternia Crystal Stand in a roughly flat terrain: a maximum of three tiles of vertical deviation is allowed, any more and the Eternia Crystal Stand will not accept the Eternia Crystal.

After the event is summoned, the player will obtain ten Etherian Mana, enough to summon one Tavernkeep sentry immediately. Two mysterious portals will also appear, and that's where the Enemies of the Event spawn. These enemies drop Etherian Mana when killed, allowing a player to summon more sentries as the event goes on.

The objective is to protect the Eternia Crystal from the enemies until all waves have been defeated.

General strategies
A completely flat arena works very well. If an enemy's path to the Eternia Crystal is blocked it will phase through obstacles, so trying to stop their progress with blocks won't be very effective. Building the floor with will greatly increase movement speed.

It's easy to get overwhelmed when fighting the enemies coming from both sides, so the player should constantly move to the left and right of the Crystal in order to prevent the enemies from reaching it and killing each side individually. They should also always be on the watch for Etherian Wyverns and Kobold Gliders, as they can quickly get to the Crystal and deal a lot of damage to it. The Tavernkeep's Sentries will deal with the weaker grounded enemies, however they are not very effective against flying enemies.

When fighting Tier 2 and 3, building a ceiling above the Eternia Crystal will protect it from Kobold Gliders, since they only explode on contact with blocks.

Tier 1
Tier one is the easiest, as it possesses the weakest enemies and only has five waves. It can only be summoned after the Eater of Worlds/Brain of Cthulhu have been defeated, as then the Tavernkeep will spawn for the first time.

The player will only see five different enemies:
 * The is the basic enemy of the event as well as the most common. It doesn't possess high stats or a special attack, making them very easy to kill.
 * The and  are stronger enemies with ranged attacks. They will start spawning on Waves 2 and 3 respectively.
 * is a high damaging enemy with the ability to fly. It will quickly fly towards the Eternia Crystal, and then it will dive towards it. It will start spawning on Wave 4.
 * The  is the Boss of the tier, spawning on Wave 5. It will alternate between shooting magical energy at the player, summoning  and healing all enemies around it. It has to be the last enemy killed in order to finish the event, but note that killing one of them does not progress the wave enough to instantly end it.

Recommended gear
While the event can be summoned at any time after defeating Eater of Worlds/Brain of Cthulhu, it's better to use the best gear available in PreHardmode.

Armor

 * provides the highest defense and good bonuses for Melee characters.
 * will give greater bonuses to Ranged characters.
 * The Wizard set with and  provides the highest stat bonuses to Mage characters.  provides higher defense.
 * A Summoner should not attempt the event without obtaining first.
 * A Thrower should get from the Desert.

Weapons
In addition to their normal weapons, all classes should also use one of the Tavernkeep's Sentries.

Melee

 * The, or the  are great weapons at close range.
 * If obtained, the can do great damage to all enemies despite its short reach.
 * The is a great weapon, but it's better suited for single targets.
 * The is great against crowds.

Ranged

 * The with  is the best gun available.
 * A with  will excel against crowds. The  can serve the same purpose.
 * The is also a very strong weapon to use.

Magic

 * The and  excel against crowds.
 * The and  are better against single targets.
 * The is an acceptable secondary weapon.

Summoner

 * At this point in the game, the best minions available are the and.

Thrower

 * ,  and  are the best throwing weapons to use for crowd control.
 * The is also an effective weapon.
 * are best for single targets.

Accessories

 * Mobility accessories such as the, variants of the and  are always good to have.
 * The provides a high damage upgrade to all weapons. The  is also good when using Bee weapons.
 * are useful to quickly regain mana as a mage.
 * can reduce damage taken.

Tier 2
After a Mechanical Boss has been defeated, the second tier of the event can be fought.

The player will find five new enemies, and the four basic enemies from the previous tier will get significantly higher stats which is reflected on their different designs.


 * are one of the new enemies found. When near the player or the Eternia Crystal, it will quickly dash towards them, exploding on contact. The explosion deals high splash damage.
 * In the later waves, the player will also find, a variant with much lower stats but the ability to fly like Etherian Wyverns.
 * have high health, defense, and knockback immunity, making them very hard to kill. They are very slow, however they will fire magical shots from a distance.
 * will surround themselves with an aura of crystals which will inflict the debuff, halving defense of players inside of it. They also possess high health, and they can regenerate damage taken.
 * The is the boss of the tier. It possesses very high damage and health, and does three dangerous attacks. From a long range, the Ogre will hurl a ball of snot at a target, it will only damage targets it hits but it will inflict the  debuff on any nearby player, slowing them down significantly. It can also jump into the air and land with a shockwave, doing area damage about ten blocks forward in each direction on the ground. At very close range, it will strike with its club, dealing very high damage. Like the Dark Mage, it needs to be killed in order to finish the event. It also drops a special accessory or item when killed.

Armor

 * is a strong choice.
 * is very good for all classes except Summoner.
 * , is a great choice due to its moderately high stats and the buff.
 * is especially useful due to its set bonus being able to hit many enemies at once.
 * may be useful due to its set bonus.
 * is the best choice for summoners.
 * should only be used if the player wants to mix summon and magic weapons, as it doesn't provide enough stat bonuses for either individual class to be useful.

Weapons
Just like in Tier one, all classes should also use one of the Tavernkeep's Sentries with their normal weapons.

Melee

 * The is the best sword available.
 * is very good for crowds.
 * The is the strongest yoyo available.
 * The is useful due to its ability to ricochet.
 * If used correctly, the can deal an extremely high amount of damage.
 * A should also be used.

Ranged

 * The and  with  are the strongest bows available.
 * The with  is very strong against single targets.
 * The or  with  or  excel against crowds, while  are better for single targets.
 * It is always good to have a secondary weapon with ammo.

Magic

 * The is excellent against crowds. The  is useful as well.
 * The is good for all enemies.
 * and are very strong against single targets.
 * The and  are very good secondary weapons.

Summoner

 * The and  are the best minions available.
 * can be used as an extra sentry.

Accessories

 * are extremely useful in hardmode.
 * Mobility accessories such as the or  are very useful as well.
 * Damage increasing accessories such as any Emblem, the or  and  are always a good choice.
 * Variants of the and  can prevent hits.
 * are still good for regaining Mana.

Tier 3
Defending the Eternia Crystal is very difficult for people that just defeated the Golem.

Melee

Arena: Campfire, Heart Lantern, and two rows of platforms about 20 blocks above the Eternia Crystal with a heart statue hooked up to a timer. A Sharpening Station is also useful.

Equipment: Shinobi Infiltrator Armor, Demonic Lightning Aura Staff (Successfully farming tier 2 thirteen times will give you the 325 Defender Medals you need to get the full set of armor and staff once golem is defeated), If Shinobi Infiltrator Armor is not available, beetle armor also works, Ruthless Staff of the Frost Hydra, Godly/Ruthless Possessed Hatchet, Godly Paladin's Hammer, Vampire Knives (if available), Star Veil, Charm of Myths, Ankh Shield, Celestial Shell, Celestial Stone, Flesh Knuckles (if available)/Frozen Turtle Shell, and Blessed Apple. Warding prefix is probably best. Useful potions include Regeneration, Ironskin, Endurance, Heartreach, and Rage/Wrath potions. Use a Flask of Ichor if available.

Strategy: Set up the lightning auras right on top of the portals and as close as possible to each other leading towards the Eternia Crystal, with two frost hydras about halfway between the portal and Eternia Crystal on each side. At some point you may want two lightning auras on the platform, one on each side of the screen, to take care of any enemies that fly above the frost hydras.

Use the Paladin's hammer to take care of the mobs and Ogres/Dark Mages, especially watch out for groups of Drakin, as they may push past the frost hydras in the early stages.

Use the potions right before the final wave, make sure the frost hydras are re-summoned, and switch to the possessed hatchet. Ignore all mobs except Etherian Wyverns spawned by Betsy. Focus on dodging and allow the hatchet to whittle Betsy down. As long as the wyverns are taken care of quickly, you should have all the time you need to finish the fight, though it will take awhile.

This strategy allows you to defeat tier 3 (and Betsy) immediately after fighting Golem, though you will need to fight him multiple times in order to get the hatchet and two Sun Stones.

Ranged

Arena: Campfire, Heart Lantern, and two rows of platforms about 20 blocks above the Eternia Crystal with a heart statue hooked up to a timer. An Ammo Box is also useful.

Equipment: Red Riding armor, Demonic Explosive Trap Staff, Ruthless Staff of the Frost Hydra, Unreal Tsunami, Stake Launcher (not necessary), Golden Shower (if available), Magic Quiver, Star Veil, Frozen Turtle Shell, Cobalt Shield variant, Celestial Shell and Charm of Myths as well as a Blessed Apple. Useful potions include Regeneration, Ironskin, Endurance, Archery and Heartreach potions.

Strategy: Set up the explosive traps right on top of the portals and immediately next to each other leading towards the Eternia Crystal, with two frost hydras about halfway between the portal and Eternia Crystal on each side. Ogres will be the only thing to take care of until the final wave, but a stake launcher is useful for clearing early waves when there aren't a lot of explosive traps since it will pierce up to ten enemies.

Use the potions right before the final wave, make sure the frost hydras are re-summoned, and switch to Holy, Venom, or Ichor arrows. Holy Arrows will rain stars on any mobs that get past the explosive traps and frost hydras (there shouldn't be any), while Venom Arrows will deal the most damage (pre-Moon Lord). If you have a crimson world, Ichor Arrows or a Golden Shower are both useful against Betsy. Ignore all mobs except Etherian Wyverns spawned by Betsy in order to focus her down. Dodging and managing health is key to winning this fight, but it should be fairly straightforward.

Magic

Arena: Flat area with Conveyor Belts on both sides of Eternia Crystal bringing Stars towards the center. Additional Buffs can help but are not necessary

Equipment: Nebula Armor, Mystic Last Prism, Ruthless Lunar Portal Staff,