The eighteen Armanen runes are Guido von List's row, published in 1908 and built on historical characters that he renamed and reinterpreted.
The character behind it
Tyr corresponds to the Younger Futhark character whose Old Norse name was tyr, the name of a god. The rune poems gloss it in terms of the god and of a guiding star, and the Old English tradition gives its equivalent a similar reading. It is among the very few runes named directly for a named deity, and the association is genuinely medieval rather than modern.
What von List did with it
He kept the T value and the name, and assigned the character a meaning within his own eighteen. Here the historical name survives essentially intact, which makes the rune a useful check on how much of the row is inherited: the name is old, the place in a row of eighteen is not.
The frame
Von List presented the eighteen as a recovered ancient Germanic priestly alphabet and set the count from the eighteen rune-charms of the Havamal. Runologists do not accept the recovery claim.
Reception
The Armanen row was taken up in volkisch circles and by National Socialist organisations in the 1930s and 1940s, and characters from the row, this one among them, were used as insignia by those organisations. That history is documented and the atlas states it rather than leaving it to be discovered elsewhere.