Of everything List devised, the Hagal figure travelled furthest, and it is a good illustration of how an invented symbol acquires the appearance of antiquity.
The claim
Hagal sits seventh of eighteen, the exact centre of the row, and List treated that position as significant. He called it the mother rune and argued that every other Armanen character could be generated from it by taking parts of its structure.
Drawn out as a six-armed hexagonal figure, the Hagal crystal, it was presented as the lattice underlying the whole cosmos: matter, spirit and the runes themselves all folded into one shape.
What the rune actually was
The historical rune is hagall, hail. All three surviving rune poems treat it as straightforwardly bad weather. The Old English poem calls it the whitest of grains, whirled from heaven and tossed by the wind; the Icelandic makes it cold grain and sickness of serpents. It is a hazard to crops.
List's reading, the hailstone as a crystalline seed containing spirit in latent form, out of which order unfolds, is an inversion. He turned a destructive thing into a generative one because his system needed a generative centre.
Where it went
The figure was taken up well beyond List's own circle. It circulated in German esoteric groups through the 1920s and 1930s, appeared among the emblems assembled in the runic material produced under the SS, and is still in use in contemporary Armanen practice and in New Age geometry, where it turns up under names having nothing to do with runes at all.
The trajectory is worth noticing. A shape invented around 1904 by a named author has been reproduced often enough, and detached from its author often enough, that it is now routinely encountered as an ancient Germanic emblem. Nothing was forged and nobody lied after the first claim; repetition did the rest.