Dryad

The Dryad is an NPC vendor that will spawn once the following criteria have been met:
 * There is an empty House.
 * You have killed one of the following bosses: Eye of Cthulhu, Eater of Worlds, Brain of Cthulhu, Skeletron, The Twins, The Destroyer, Skeletron Prime, Ocram, Plantera, or Golem.(Not the Wall of Flesh,Lepus or King Slime.)

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

Items sold
Once the Dryad has moved into a house, she will sell the following:

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".


 * If the world has more Hallow than Corruption, she will say "Keep up the good work!".
 * If the world has no Corruption or Crimson, she will say "You have done an amazing job!".
 * If at least 20% of the world is Hallow, and more Hallow than Corruption, she will say, "We are living in a fairy tale."
 * If at least 20% of the world is Corruption or Crimson, and more Corruption/Crimson than Hallow, she will either say, "You have a lot of work to do," or "Things are grim indeed."
 * If there is very little Corruption or Crimson in the world, she will say, "You are so close!".
 * When Corruption/Crimson and Hallow percentages are similar, she will say, "The world is in balance".
 * In all other cases, she will say, "You should try harder."

However, after using the Clentaminator and spreading Corruption in a Crimson world (or Crimson in a Corruption world), she will say "[World Name] is x% hallow, x% corrupt, and x% crimson. [One of the quotes above]"

Names
The Dryad may have any of the following names:

Trivia

 * Nissa, one of the Dryad's possible names, is a possible reference to Nissa Revane, an elven Planeswalker from the Magic the Gathering trading card game
 * If a world has an artificial corruption/crimson different from the natural corruption/crimson, the Dryad will address both, even separating them with commas when the Hallow is also present.
 * One of the Dryad's possible names, Chryseis, is a character in the Iliad. She was the daughter of a priest named Chryses (her name literally meaning Chryses' daughter) and was kidnapped by Agamemnon, and eventually rescued by Odysseus. (Something like that, anyway)
 * One of the Dryad's possible names, Isis, is the name of the Egyptian mother-goddess.
 * One of the Dryad's names is Celestia, the name of the ruler in My Little Pony: Friendship is Magic. This may be a coincidence.

Quotes
Only during a Blood Moon:
 * "Be safe; Terraria needs you!"
 * "You must cleanse the world of this corruption."(Corruption world only.)
 * "You must cleanse the world of this crimson."(Crimson world only.)
 * "The sands of time are flowing. And well, you are not aging very gracefully"
 * "What's this about me having more 'bark' than bite?"
 * "So two goblins walk into a bar, and one says to the other, 'Want to get a Goblet of beer?!'"
 * "Why does [Name of Merchant] keep trying to sell me an angel statues? Everyone knows that they don't do anything." (Only if Merchant is present)
 * "I wish [Name of Arms Dealer] would stop flirting with me. Doesn't he realize I'm 500 years old?" (Only if Arms Dealer is present)
 * "Have you tried using purification powder on the ebonstone of The Corruption?" (Only if the Eater of Worlds has NOT been defeated - Corruption world only.)
 * "Have you tried using purification powder on the Crimstone of the Crimson"? (Only if the Brain of Cthulhu has NOT been defeated - Crimson world only.)
 * "Have you seen the old man walking around the dungeon? He doesn't look well at all..." (Only if Skeletron has NOT been defeated)
 * "I feel like [Name of Truffle] is a bit misunderstood, he really is a fun guy." (Only if Truffle NPC is present) (Reference to the "fungi" joke)
 * "I sell what I want! If you don't like it, too bad."
 * "Dude, is it just me or are there a million zombies out tonight?" (Even if you are a girl character)
 * "I don't want you to buy my stuff. I want you to want to buy my stuff, ok?"
 * "Why do you have to be so confrontational during a time like this?"

When asking for the status
 * "[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, and will only tell the hallow's percent after the Wall of Flesh is defeated.)

Once the world is completely pure:
 * "[Name of World] is completely pure. You have done an amazing job!"