Goat Ko.
Terrarian
I bet a lot of people including me has problems with the event. Many players fail when Betsy comes, it's hard to attack a dragon and other enemies at once huh? Well, here's a guide on how to beat it with all classes (expect thrower 
), both on expert and normal mode.
Before you read this, let me tell you that you need endgame gear!
Arena
If you don't mind a
Dryad should move under your Crystal Stand so you have more defense and life regen.
There is no much to do with an Old One's Army arena. Flat out your arena, and from the center of the Crystal Stand, make at least 61 tiles long space so that the crystal can start the event. You can make your area bigger, if you are struggling with the close portals. Here's some pros and cons for the minimal sized flat area.
Pros
-You can see the enemies more easily, and the piercing projectiles will more likely to hurt them.
-You need to move less meaning you can focus on only the enemies near the Crystal Stand.
Cons
-Enemies take less time to reach the Crystal
-Enemies that can throw/spit projectiles will get near the Crystal faster, meaning that you need to pay more attention to them.
You should also place Heart Lanterns and Campfires (Star Bottles too if you are a Mage) in your arena.
Gear
Every class' preferred gear will be listed here.
Accessories
-Charm of Myths will be useful against Betsy, due to it shortens the duration of the Potion Sickness debuff and provides +0.5 health every second.
-Yoyo bag if you are using the Terrarian will make it pretty overpowered.
-Mana Flower is a must-have for mages.
-Sniper Scope is useful for rangers.
-Any summoner accessory is good for summoners.
-Celestial Stone or Celestial Shell. Shell is more advised because it grants even more bonuses while it's nighttime, so you should fight the Old One's Army at night, if you have a Celestial Shell. If you can, wear them both.
-Solar Flare or Stardust wings, as they have the most flight time.
If you play in expert mode, and still have one accessory slot left:
-Cobalt Shield, Obsidian Shield or Ankh Shield is useful because they prevent you from getting knocked back.
All accessories should be reforged to Lucky or Menacing in normal mode, and Warding in expert (or the normal mode options if you feel them better)
Armor
-Solar Flare armor for Melee users
-Vortex armor for Rangers
-Nebula armor for Mages
-Stardust armor for Summoners
Weapons
-Melee users should use: -Terrarian, it's homing and high-damage projectiles will reap.
-Meowmere, as it's projectiles can bounce and pierce, meaning you can kill an entire line of enemies.
-Star Wrath is a god-sent gift for the enemies that are near your cursor. They will probably die.
-Vampire Knives can be used to heal, though every class can use this to heal...
-Rangers' best options are: -S.D.M.G. with luminite bullets (for the enemies) and chlorophyte bullets (for Betsy or Ogres) has a high DPS, as the luminite bullets can pierce infinitely, and the chlorophyte bullets will home on enemies.
-Celebration. A lot of people underestimate it, but that's a bad thing. It has a surprisingly high DPS, especially with Rocket V-s
-Mages will be probably the most overpowered, if not the summoners: -Last Prism has piercing and almost the highest DPS of any weapon in the game. If combined with the Mana Flower accessory and mana potions, the event should be pretty straight-forward. You can also dig holes under the arena, place statues that can spawn enemies, wire them to a one-second timer and summon ravens (acquired from the Pumpkin Moon event) in the holes, so Mana Stars will spawns, which will prevent you from getting the Mana Sickness debuff.
-Summoners' best option is the: -Stardust Dragon staff, with it's damage scaling it can reach pretty high DPS.
All the weapons should be reforged to the best possible modifiers, unless that mean goblin steals them all.
Strategy
Have Super Healing Potions in your inventory, if you need to insta-heal, you can use them to heal back 200 health.
This strategy is pretty simple: use the piercing weapon (if you have one) or other mass murderer weapons, and use the others on Betsy.
It's quite hard to dodge Betsy's attacks, but try to dodge them.
Also, if enemies begin to attack the Crystal while you fight Betsy, kill them, don't ignore them. Betsy will most likely focus on you and not the Crystal.
That's it, this was my first guide ever. I had a lot of time creating this, and I hope this helps you. Good luck!
), both on expert and normal mode.Before you read this, let me tell you that you need endgame gear!
Arena
If you don't mind a
Dryad should move under your Crystal Stand so you have more defense and life regen.There is no much to do with an Old One's Army arena. Flat out your arena, and from the center of the Crystal Stand, make at least 61 tiles long space so that the crystal can start the event. You can make your area bigger, if you are struggling with the close portals. Here's some pros and cons for the minimal sized flat area.
Pros
-You can see the enemies more easily, and the piercing projectiles will more likely to hurt them.
-You need to move less meaning you can focus on only the enemies near the Crystal Stand.
Cons
-Enemies take less time to reach the Crystal
-Enemies that can throw/spit projectiles will get near the Crystal faster, meaning that you need to pay more attention to them.
You should also place Heart Lanterns and Campfires (Star Bottles too if you are a Mage) in your arena.
Gear
Every class' preferred gear will be listed here.
Accessories
-Charm of Myths will be useful against Betsy, due to it shortens the duration of the Potion Sickness debuff and provides +0.5 health every second.
-Yoyo bag if you are using the Terrarian will make it pretty overpowered.
-Mana Flower is a must-have for mages.
-Sniper Scope is useful for rangers.
-Any summoner accessory is good for summoners.
-Celestial Stone or Celestial Shell. Shell is more advised because it grants even more bonuses while it's nighttime, so you should fight the Old One's Army at night, if you have a Celestial Shell. If you can, wear them both.
-Solar Flare or Stardust wings, as they have the most flight time.
If you play in expert mode, and still have one accessory slot left:
-Cobalt Shield, Obsidian Shield or Ankh Shield is useful because they prevent you from getting knocked back.
All accessories should be reforged to Lucky or Menacing in normal mode, and Warding in expert (or the normal mode options if you feel them better)
Armor
-Solar Flare armor for Melee users
-Vortex armor for Rangers
-Nebula armor for Mages
-Stardust armor for Summoners
Weapons
-Melee users should use: -Terrarian, it's homing and high-damage projectiles will reap.
-Meowmere, as it's projectiles can bounce and pierce, meaning you can kill an entire line of enemies.
-Star Wrath is a god-sent gift for the enemies that are near your cursor. They will probably die.
-Vampire Knives can be used to heal, though every class can use this to heal...
-Rangers' best options are: -S.D.M.G. with luminite bullets (for the enemies) and chlorophyte bullets (for Betsy or Ogres) has a high DPS, as the luminite bullets can pierce infinitely, and the chlorophyte bullets will home on enemies.
-Celebration. A lot of people underestimate it, but that's a bad thing. It has a surprisingly high DPS, especially with Rocket V-s
-Mages will be probably the most overpowered, if not the summoners: -Last Prism has piercing and almost the highest DPS of any weapon in the game. If combined with the Mana Flower accessory and mana potions, the event should be pretty straight-forward. You can also dig holes under the arena, place statues that can spawn enemies, wire them to a one-second timer and summon ravens (acquired from the Pumpkin Moon event) in the holes, so Mana Stars will spawns, which will prevent you from getting the Mana Sickness debuff.
-Summoners' best option is the: -Stardust Dragon staff, with it's damage scaling it can reach pretty high DPS.
All the weapons should be reforged to the best possible modifiers, unless that mean goblin steals them all.
Strategy
Have Super Healing Potions in your inventory, if you need to insta-heal, you can use them to heal back 200 health.
This strategy is pretty simple: use the piercing weapon (if you have one) or other mass murderer weapons, and use the others on Betsy.
It's quite hard to dodge Betsy's attacks, but try to dodge them.
Also, if enemies begin to attack the Crystal while you fight Betsy, kill them, don't ignore them. Betsy will most likely focus on you and not the Crystal.
That's it, this was my first guide ever. I had a lot of time creating this, and I hope this helps you. Good luck!