Dryad

The Dryad is an NPC vendor that will spawn once the following criteria have been met:
 * There is an empty House.
 * Any boss has been defeated (excluding King Slime, Wall of Flesh, and ).

In addition to selling items, the Dryad can report the percentages of Corruption/Crimson vs. Hallow that exist in the current world.

When enemies are nearby, the Dryad will periodically grant the Dryad's Blessing buff to players in the vicinity and displays a leaf barrier effect. The buff grants +8 defense, and gives the player contact damage. Enemies touching the leaf circle of the barrier will take 1 point of damage per second, more if you defeated more bosses (and x1.5 during Expert mode).

World status
The Dryad's reports on Corruption/Crimson/Hallow coverage are accompanied by a status message. She considers Hallow "good", and Corruption or Crimson "bad". The Dryad makes the distinction between Corruption and Crimson if they are present in the same world, and will list their percentages separately, though they both contribute to the overall "bad" total in her final report.

Tips

 * For players creating housing for the Truffle, it would be beneficial to temporarily house the Dryad in or near a Mushroom biome where she will sell Mushroom Seeds.
 * If you can't build a house you can use a Queen Statue to teleport her to a Mushroom biome.
 * Another way to get Mushroom Seeds is to use Boulders or Land Mines to kill the Dryad and make the only valid house in a Mushroom biome.

Names
The Dryad may have any of the following names:

Quotes
After defeating Old One's Army:
 * Tier 1:
 * "" [sic]
 * Tier 2:

When Merchant is present: When Arms Dealer is present: When Truffle is present: Before Skeletron is defeated: In a Corrupt world:
 * "" [sic]
 * Before defeating the Eater of Worlds
 * Before defeating the Eater of Worlds

In a Crimson world:
 * Before defeating the Brain of Cthulhu:
 * Before defeating the Brain of Cthulhu:

Only during a Blood Moon: When asking for the status Once the world is completely pure: During a party:
 * "[Name of world] is [hallow percentage]% hallow and [crimson/corruption percentage]% [crimson/corruption]. [Dryad's comment, see above]."(She will say crimson or corruption depending on which one there is, however if you have corruption and make an artificial crimson biome, she will list both crimson and corrupt percentages, as well as vice versa. She will tell the hallow's percentage in Hardmode.)

Trivia

 * A is a nature spirit from Greek mythology, generally depicted as a beautiful young woman. Fittingly, many of the Dryad's possible names take inspiration from either classical literature (e.g., , , ) or female celebrities.
 * This might be the reason that the Arms Dealer appears to flirt with her as shown in one of his quotes, but she states in one of her quotes that she wishes the Arms Dealer would stop pestering her.
 * In the same quote she reveals that she is 500 years old.
 * The Dryad is depicted in a Painting called Dryadisque.
 * Her quote calling the Truffle a "fun guy" plays on the "".
 * One of the Dryad's quotes about the player's safety says "Terraria needs you," instead of "[World Name] needs you." This is an oddity among the other quotes.
 * Calista the Dryad is featured in the Terraria Comic Book from DC Comics.
 * The Dryad also appears in Dungeon Defenders II.
 * The Dryad's quote referencing her time in Etheria and her use of the corruption against the Old One's Army is a reference to her ability in Dungeon Defenders 2 where she can become a corrupted version of herself to do extra damage.
 * One of The Dryad's names (Nissa) comes from the planeswalker Nissa Revane from the trading card game,.
 * According to the official game lore, an ancient race of Dryads once waged a large war with Cthulhu. Unable to defeat the beast, they crippled him by ripping out vital chunks of its body. However, only one Dryad remains, this being the NPC you obtain in-game.

History
Dryade Dryade 드라이어드 树妖