Nymph

The Nymph is a rare enemy that spawns underground. When first encountered, it appears as the Lost Girl, who pretends to be a helpless NPC that needs to be saved. When a player gets close, it transforms and attacks as the Nymph, a dangerous enemy that deals high damage (for a pre-Hardmode enemy). It is arguably the rarest creature in Terraria and is extremely hard to find.

Tips

 * It cannot attack from a distance, nor can it jump very high. Use a ranged weapon from an out-of-reach position.
 * A Harpoon or Flail can be effective, as Nymphs can be stun-locked. Even with its high health, the Harpoon can kill a Nymph in moments with no risk to the wielder, due to its extremely high rate of fire, so long as it is used at short range.
 * Any high rate of fire weapon will be very effective, as they cannot approach you enough for their attacks to hit.

Trivia

 * The Lost Girl appears completely naked. Ironically, it appears often in underground snow biomes, as if it is immune to the cold.
 * In Greek and Latin mythology, a nymph is a lesser female deity with the power to animate nature. The behavior of Terraria's nymphs (i.e. luring players in before attacking them) is more similar to that of the siren, another creature from Greek mythology.
 * Could be inspired by numerous characters in popular culture that bait heroes by appearing harmless and in need of assistance.
 * The left half of the Nymph Banner is of the Lost Girl NPC, while the right half is the Nymph monster.
 * In the Spider Nest there is a background object with an unknown, bound NPC which could be a possible reference to the actual lost girl.