Guide:Defending against invasion events

Overview
This guide deals with the events currently implemented in version 1.2 of Terraria.

Blood Moons
Blood Moons are rather frequent events that can be a hassle for newer players who are caught unaware. Not only does the monster spawn rate increase dramatically during a Blood Moon, but the max amount of enemies that can be on screen also rises significantly, allowing swarms of enemies to appear at one time. Additionally, zombies can break open doors during this event, posing significant danger to NPCs inside houses. However, there are ways to profit from Blood Moons if one is prepared, especially thanks to rare spawns like The Groom.

Frost Legion
There are three unique monsters in the Frost Legion, named Mister Stabby, Snowman Gangsta, and Snow Balla. The Frost Legion does not happen on its own. The player has to obtain a Snow Globe from a Present to summon them. The summon item can only be obtained in Hardmode, but the Legion can still be summoned and defeated in a non-Hardmode world.

Frost Moon
The enemies during a Frost Moon are very dangerous, being essentially stronger versions of the Pumpkin Moon enemies. The player has to craft a Naughty Present to start a Frost Moon.

Due to the fact that this event is EXTREMELY hard, it is highly recommended (if not outright mandatory) to wear top-notch end-game equipment. It is furthermore highly advised to build an arena with traps (Lihzahrd-type ones) and lava to help deal with the waves of monsters, much in the same manner as with the Pumpkin Moon. The arena should also feature a nearby house serving as a spawn-point for dead players. Wounded monsters will regain full life if the house is too far away. The event lasts throughout the night only and will end on 4:30am, making high damage a must to properly advance and obtain loot.

Mage set: The mage set is perhaps the most powerful set due to the armor's ability to heal the caster and his/her allies. Despite making the wearer somewhat fragile, the healing output has the potential to usually pull through. With the game featuring some powerful magical weapons, the mage set can provide the greatest healing currently possible (surpassing the Vampire Knives). This makes it very nifty for multi-player and extremely recommended for single-player. The currently best magic weapons are the Blizzard Staff, Bubble Gun, and Razorpine, though with these coming from the Frost Moon itself (save for the Bubble Gun, which is dropped by Duke Fishron,) the player may try obtain any of the other weapons first. It should be noted that although the Nimbus Rod provides great damage, its mechanic makes it more of an assisting weapon. The Razorblade Typhoon not only pierces infinitely, but also is a homing weapon, making it an excellent choice for crowd control or fighting the Ice Queen. Also note that if you cannot afford the vast amounts of Greater Mana Potion/Super Mana Potion that is required for sustaining your mana, you may also arguably swap the Avenger Emblem/Mechanical Glove for Magic Cuffs/Celestial Cuffs.
 * Armor: Spectre armor (with Spectre Hood)
 * Weapons: Nimbus Rod, Heat Ray, Inferno Fork, Bat Scepter, Razorpine, Blizzard Staff, Bubble Gun, Razorblade Typhoon
 * Accessories: Destroyer Emblem, Sorcerer Emblem, Celestial Emblem, Avenger Emblem/Celestial Stone, Star Veil

For a good way to take on the Frost Moon as a mage, see YouTube: "Terraria: Frost Moon Final Wave SOLO (Mage Loadout | Arena Download")

Note: As of the 1.2.3 patch, the Mage approach has received two heavy nerfs. The first is the Spectre Hood now reducing magic damage by 40%, the second that consuming a mana potion causes Mana Sickness. This has undoubtedly reduced the capability of this tactic quite a bit. The latter nerf has likely made any "Cuffs" accessory of much greater convenience.

Ranged set: The ranged set is likely capable of lashing out the most damage. With the proper gear and a suitable positioning (to trigger/keep the armor's ability), chances are good the player can utterly destroy any incoming enemies near instantly. The ranged set does however not supply any sort of healing, and is thus more dependent on multiplayer support or an arena designed to prevent enemies from being able to deal contact damage, along with blocking enemy attacks. Exploding Bullets are recommended, as they deal damage twice on a direct hit, which can be used with a Sniper Rifle to kill most non-boss enemies in very few shots, often 1 or 2, along with damaging nearby enemies.
 * Armor: Shroomite armor (with a helmet variant that benefits your weapon)
 * Weapons: Candy Corn Rifle, Rocket Launcher (using Rocket III for ammo), Stynger, Snowman Cannon, Chain Gun or Tactical Shotgun (using Exploding Bullets for ammo)
 * Accessories: Destroyer Emblem/Sniper Scope, Ranger Emblem, Avenger Emblem, Celestial Stone, Star Veil

Melee damage set: For soloing purposes, there appears to be two approaches with a melee damage set:
 * Armor: Beetle armor (with Beetle Scale Mail)
 * Weapons: Vampire Knives, The Horseman's Blade
 * Destroyer Emblem, Warrior Emblem, Avenger Emblem/Mechanical Glove/Celestial Stone/Fire Gauntlet, Star Veil
 * Vampire Knives: This method aims to sustain the player's life through the Vampire Knives. Though it is weaker than the mage set it is powerful enough (much due to the high armor) to survive several waves of the Pumpkin Moon and Frost Moon events, and can thus be used as a stepping stone to obtain weapons for other sets (such as Razorpine or the Blizzard Staff).

The melee damage set does not have much appeal in multi-player. The Vampire Knives do not heal allies and both its and the The Horseman's Blade's damage are likely to be outdone by that of the ranged and mage sets. At best it may offer some entertainment as another way of dealing damage. In this case the set may also benefit from weapons such as the Christmas Tree Sword and North Pole - given the player is healed by a mage.
 * The Horseman's Blade: This method relies of the The Horseman's Blade's ability to spawn homing pumpkins. It is dependent on a cluster of statues to spawn weak monsters, much like an ordinary statue farm. See YouTube: Terraria - Frost Moon Event Melee (Wave 15) for a video of this method.

Tanking set: The tanking set is, like the ranged set, aimed at multi-player. Its purpose is to direct monsters' attention so that more fragile characters can butcher them all. For this reason the set has a high value of defense, and consequently lesser damage than the other sets. If, during multi-player, the overall healing is good enough, some defense-granting accessories may arguably be replaced by damaging-increasing ones, such as those used by the melee-damage set. The weapon can similarly be something else than the Vampire Knives. Though the player probably won't die that often, this set is unlikely to perform well in single-player due to how the low damage won't allow for much wave advancement.
 * Armor: Beetle armor (with Beetle Shell)
 * Weapons: Vampire Knives
 * Accessories: Paladin's Shield, Frozen Turtle Shell, Star Veil, Celestial Stone, Ankh Shield

Notes: ¹ These items increase monster spawn. This will allow for more killing, which improves wave advancement.
 * All players should buff themselves during the fight. Suggested items to buff with are:
 * Potions: Any Well Fed-item, Battle Potion¹, Ironskin Potion, Regeneration Potion, Swiftness Potion, Thorns Potion, Shine Potion², Night Owl Potion², Hunter Potion²
 * Melee: Ale, any Flask (preferably Ichor), Obsidian Skin Potion (melee players are likely to touch the lava)
 * Ranged: Archery Potion (only if the player uses a bow or repeater)
 * Mage: Magic Power Potion, Mana Regeneration Potion
 * Stationary: Campfire, Heart Lantern, Water Candle¹, Crystal Ball (for mages), Ammo Box (for ranged users), Honey³
 * Other: Wisp in a Bottle², Fairy Bell²

 ² These items help you see monsters, but can likely be omitted without much consequence.

³ As the honey buff is obtained by touching honey, its uptime may be tricky to maintain.
 * In addition to buff potions, players should also bring Greater Healing Potions and Super Mana Potions. As the latter is likely to be consumed in extreme quantity, the player should bring vast amounts.
 * Please note that all the mentioned accessories above are recommended to have good modifiers, if not the best.
 * The mage, ranged, and melee damage sets should have Menacing (4%+ damage) or Lucky (4%+ critical strike chance) and the tanking set should have Warding (4+ Defense).
 * The Star Veil's (and the Cross Necklace's) ability to increase the player's invincibility after taking damage is crucial to this fight. Without it, the player is unlikely to survive for long.
 * A Wings accessory is not mandatory, but can be of help. They will not see much use until Ice Queen shows up, at which point they can be used for chasing her and dodging her attacks.
 * The Vampire Knives will not work properly on targets under constant damage, such as when standing in lava or below a Nimbus Rod-cloud. A way to solve this is by making an arena in which the player is partly surrounded by a large rectangle of blocks. The Everscreams and Santa-NK1s will be able to pass through the wall and rise to the "floor" of it, (thus getting above the lava) at which point the Knives can hurt them, while the other monsters are kept outside/below the rectangle and have to remain in the lava.

Goblin Army
Goblins will appear at the spawn point and kill any NPCs they find. They will continually spawn until their army limit is reached before the event will end. This group has multiple types of units with different attack patterns, so strategies for dealing with them will differ depending on the type of goblin.

The Goblin Sorcerer will teleport no matter where the player(s) are and will shoot a projectile at you.

The Goblin Thief is a fast paced enemy that will deal a lot of damage if you are still.

The Goblin Peon is like the Goblin Thief but is a little slower than it and will not do that much damage if you have the best armor and defense.

The Goblin Warrior has armor that will not kill in one shot but will do heavy damage to the player(s). The Goblin Archer shoots arrows at the player(s) until they die and will deal decent damage to the player.

The Goblin Scout doesn't have that much defense and will die in one shot if the best weapons are used. They drop Tattered Cloth which is used to make the Goblin Battle Standard. These goblins do not spawn during the invasion, and can only spawn at the edges of the world.

Pirate Invasion
The Pirate Invasion is very similar to the Goblin Army, except the pirate invasion can only be triggered in hardmode, and is much harder than the Goblin Army. The Pirate Invasion has multiple types of units with different attack patterns.

Pumpkin Moon
The enemies during a Pumpkin Moon are very dangerous, especially The Headless Horseman and Pumpking. The player has to craft a Pumpkin Moon Medallion to start a Pumpkin Moon.

Solar Eclipse
The monsters spawned during a Solar Eclipse are very powerful. The Reaper acts similarly to a Wraith, but with higher stats. The Swamp Things are extremely fast, and they are as common as zombies. Vampires are equally as common as zombies, and can turn into bats if the player is above them. Eyezors are not very common during a Solar Eclipse, but they can shoot lasers from their eyes, making them formidable enimies. They are slightly faster than regular zombies. Frankensteins are common as zombies, but move much faster.

Methods
Generally, Blood Moons can be seen safely through by simply holing up in your base, as long as all doors are either prevented from opening inwards or simply barracaded by blocks. Blood Moons do not spawn truly dangerous enemies; they simply increase the spawn rate and maximum onscreen limit while introducing a few rare variations such as Corrupt Bunnies and Corrupt Goldfish. This means that players who are adept at handling zombies and Demon Eyes have little to fear from this event, and can actually profit by it.

The Goblin Army's members do not specifically attempt to hunt down and kill NPCs; rather, that is just a side effect of them spawning near the player's starting point and attacking the player. If the player is strong enough to easily handle the goblins, a long, flat field near the base would be the best place to deal with the army, as it would be close enough to the spawn point to appear while keeping the goblins away from the NPCs. This assumes, of course, that the player is strong enough to deal with the swath of continually spawning goblins and willing to engage them in plain-old mano-a-goblin fighting. Check the article on the Goblin Army.It already has several methods for dealing with them.

The Solar Eclipse strategy is simple to understand. Every enemy but the Reapers and Vampires use standard Fighter AI, (and even the same jump range as basic Zombies and Goblins,) and will walk into pits just like any other zombie. Lava pit traps will destroy the whole invasion force but the reapers. Hence, the easiest way to nullify most of the threat is to dig a simple tunnel underneath a small lava pit on some leveled terrain. That allows players to simply focus on fighting the Reapers alone, (which are rare enough that you rarely fight more than one at a time,) while collecting all the drops. Check the article on the Solar Eclipse. It already has several methods for dealing with them.

For the Frost Legion,if you're far enough underground then the snowmen won't spawn, even after getting the message that they've arrived, so you don't have to head back to your house immediately upon receiving message of an imminent attack. However, they will remain and will appear if you surface. The Snowmen are incapable of jumping down from simple wooden platforms, meaning it is possible to construct a basic trench with a wooden platform above it, and be completely out of harms way. If you place lava pits on either side of your house, you can defeat most of the snowmen that spawn, however, Snow Ballas may block up the traps, inhibiting the trap from killing any more snowmen. Filling the empty space of any traps with Wooden Beams will prevent Snow Ballas from blocking up the traps. The beams occupy the same layer as other furniture and do not block movement.

For the Pumpkin Moon, since the wave number increases based on the number of enemies killed, taking a Battle Potion to increase the spawn rate is highly advised. If this is done, the player should bring two potions into battle, since one of them taken at the beginning of the night will wear off about halfway in. Most Pumpkin Moon enemies are susceptible to the Ichor Debuff, making a Flask of Ichor or the Golden Shower spell very valuable for this event.

For the Pirate Invasion, if you want to face the pirates head-on you must be prepared. Defeating these pirates is not an easy feat for a fresh hardmode player. You will want to use weapons that pierces multiple enemies at once, such as the Shadowbeam Staff or the Magical Harp. Alternatively, you can make sure the pirates stay below you, with you on a wooden platform. Then use some kind of high-level Spear to slay the attackers. When a captain attacks, focus all of your attention on him, because he will stop attacking when attacked. If you have the Uzi, Flamethrower, or Minishark/Megashark it is good to continually fly over the pirates and shoot at them as it is hard for them to shoot you down. Check the article on the Pirate Invasion. It already has several methods for dealing with them.

Lava
Lava is a useful tool to help thin out the numbers of enemies. Making shallow pools of lava is a common way to burn enemies to death while allowing their item drops to collect as they approach your home. Other variations include "waterfalls" of lava or even entire moats, albeit using large bodies of lava means any item drops will be destroyed as well, though it is always fun to watch zombies pour into a pit of lava en masse. It is possible to get the lava to a low enough depth that enemies are burnt but items are not, and can be tested by throwing a low value item (copper coins can be useful) into the pool, and seeing if it disappears.

Spiky Ball Trap Moat
Similar to the lava pool is the Spiky Ball Trap Moat. If you have recovered spiky ball traps from the Lihzahrd Dungeon, you may dig a moat completely under your house. The moat should be at least 12 blocks deep. Next, mount spiky ball traps to the underside of your house at regular intervals. Connect the spiky ball traps to a 3 second timer inside your house. Activate the timer once the invasion begins to rain down spiky balls on the Goblin Army.

Dart Trap
Although they do not deal a lot of damage, dart traps or Lihzard Super Dart Traps are an easy-to-use method of defending your base - all you have to do is set them up on the outside of your entrances and set up manual triggers using switches or levers, or automatic triggers such as pressure plates or timers. It is a good way to keep the weaker enemies out of your base, although it is more of an offensive technique than a defensive one. If you're using one of the aforementioned automatic techniques, you should be careful not to let you or your NPC villagers get shot when going out of their houses.

Active Stone Blocks and Actuators
If you have the mechanic its easy. Place the active stone block one side of the door and wire it to a switch and it block zombies and most goblins, or even make the "door" out of active blocks and turn them off when you need to go through. The same effect can be achieved with actuators.

By using actuators and Grey, Brown, Blue or Lihzahrd pressure plates, you can create a player only door that doesn't even require you to use your mouse. Setup the door as you would an active stone/actuator door and because Grey, Brown, Blue or Lihzahrd pressure plates can only be activated by the player no mobs are able to enter (nor escape). Also using hellstone for the door creates a great defence as it will provide (slow) damage for you.

Pit
Digging a pit on both sides of your base is a simple but effective way of holding back most of the goblins, save for sorcerer and archer goblins. The nice thing about pits when compared to the other methods is that you don't need any items found in midgame pre-hardmode like lava or finding the mechanic. Just simply dig a hole five deep by six wide or dig the pit next to a wall so when the goblins try to jump the pit they will hit the wall and fall into the pit. The downside to using a pit by itself, (without lava or other traps), is that after taking out the sorcerers and archers you still need to take care of the goblins in the pit. However, you can use the spikeballs dropped from the goblins you killed earlier and throw them into the pit to take them out from a safe distance.