Aletheia (Heraclitus, Fragment B 16)

But the golden gleam of the lighting's invisible shining cannot be grasped, because it is not itself something grasping. Rather, it is the purely appropriating event [das reine Ereignen]. The invisible shining of the lighting streams from wholesome self-keeping in the self-restraining preservation of destiny. Therefore the shining of the lighting is in itself at the same time a self-veiling—and is in that sense what is most obscure.

Heraclitus is called ὁ Σκοτεινός. He will also retain this name in the future. He is the Obscure, because he thinks questioningly into the lighting.

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