Dai Li- The Dai Li are the "cultural protectors of Ba Sing Se," as mentioned by Joo Dee in Book 2: Earth, Chapter 14: The City of Walls and Secrets. They are very skilled earthbenders, which make them dangerous, especially in a group. They were originally led by Long Feng, and followed him without question. After, meeting Azula they started to question who would be fit to rule Ba Sing Se. Azula refers to them as having a killer instinct that's so firebender, and she just loves it. The people who have actually fought the Dai Li, are Aang, Katara, Sokka, Toph, Jet, Smeller Bee, Long Shot, and even Iroh for a very short time. The Dai Li seem to have gloves made of earth(rock), in which they can extend to capture enemies from afar.
Other Sources: Long Feng, Azula, Ba Sing Se, etc.
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