Betsy

Betsy is a Hardmode, post-Golem boss that spawns in the last wave of the Old One's Army event, wave 7. She attacks by flying, charging, and spewing projectiles from above. Like all enemies in the Old One's Army, she will despawn upon completion or failure of the event.

Behavior

 * Betsy alternates between four attacks:
 * She flies in a large loop, before dashing at the player multiple times.
 * She moves to the edge of the screen, and flies horizontally across the screen, breathing a constant stream of fire downwards.
 * She launches many smaller fireballs that are affected by gravity, similar to the attack of Betsy's Wrath. However, they do not inflict debuffs.
 * She stands in place and roars. Two Etherian Wyverns will then appear beside her. Four Etherian Wyverns will also spawn from either portal when she does this.

Tips

 * The On Fire! debuff is a major source of damage. Note that it negates life regen from Nebula armor's set bonus – hence, if the player is unable to avoid Betsy's flame breath attack, it might make the armor ineffective.
 * The Obsidian Skin Potion can prevent the debuff.
 * A floating pool of water (utilizing Bubbles) can be used to cancel the On Fire! debuff. Honey will also cancel the debuff and also give extra life regeneration, but slows down movement while submerged in it.
 * This does not apply to life-stealing effects such as the Spectre armor Hood set bonus or the Vampire Knives. It does not affect the Life Drain's health regen boost either.

Trivia

 * The boss is based on the Betsy boss from Dungeon Defenders 2, as the 1.3.4 update brought a crossover event between the two games.
 * Betsy is the only event boss to drop a Treasure Bag in Expert mode, and the only boss whose Treasure Bag does not contain Expert-exclusive items.
 * Betsy's attack behavior of flying and launching projectiles is fairly similar to Duke Fishron's. Unlike Duke Fishron, however, she does not have additional phases as a boss.
 * Betsy is one of the only enemies of the Old One's Army to focus on the player instead of the Eternia Crystal.
 * She is one of the two enemies that resemble s but do not possess the Worm AI, the other being the Etherian Wyvern. The reason is that they have no segments and are instead counted as single enemies.

History
Betsy 双足翼龙