Golfing Chain (Robbers' Thread)
Brain-Flak, 90 bytes by Mr. Xcoder

((((((((((()()()){}){}){({}[()])}{}())[(((()()()){})){}{}()]))){}{}()()())([][][]){})[][])


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This outputs:

ÑÉ·&lt;O


First 05AB1E answer!

How does it work?

Let's say we have 24 as input.

Ñ       # Divisors. 
        # Stack: [1, 2, 3, 4, 6, 8, 12, 24]
 É      # Odd?
        # Stack: [1, 0, 1, 0, 0, 0, 0, 0]
  ·     # Double
        # Stack: [2, 0, 2, 0, 0, 0, 0, 0]
   &lt;    # Decrement
        # Stack: [1, -1, 1, -1, -1, -1, -1, -1]
    O   # Sum
        # Stack: -4


The brain-flak code mostly just uses tricks to push large numbers in few bytes. It was very convenient (and unintentional) that the ASCII values are mostly increasing:

209
201
183
60
79


It's also nice that 60 * 3 ~=~ 183 so tripling it and adding a few can save a ton of bytes.

((((((

    # Push 79
    ((((()()()){}){}){({}[()])}{}())
    # Minus 19 (60)

    [(((()()()){})){}{}()])
    # Push that two extra times
    ))

    # Push that ^ (60) Plus the two extras popped (60 + 120 == 180)...
    {}{}
    # + 3 (183)
    ()()())

    # Plus stack-height * 3 * 2 == 3 * 3 * 2 == 18 (201)
    ([][][]){})

    # Plus stack-height * 2 == 4 * 2 == 8 (209)
    [][])