There is some evidence that, in addition to being a writing system, runes historically served purposes of magic. This is the case from earliest epigraphic evidence of the Roman to Germanic Iron Age, with non-linguistic inscriptions and the alu word. An erilaz appears to have been a person versed in runes, including their magic applications.
In medieval sources, notably the Poetic Edda, the Sigrdrífumál mentions "victory runes" to be carved on a sword, "some on the grasp and some on the inlay, and name Tyr twice."
In early modern and modern times, related folklore and superstition is recorded in the form of the Icelandic magical staves. In the early 20th century, Germanic mysticism coins new forms of "runic magic", some of which were continued or developed further by contemporary adherents of Germanic Neopaganism. Modern systems of runic divination are based on Hermeticism, classical Occultism, and the I Ching.
Historically it is known that the Germanic peoples used various forms of divination and means of reading omens. Tacitus (Germania 10) gives a detailed account (98AD):
It is often debated whether "signs" refers specifically to runes or to other marks; both interpretations are plausible and Tacitus does not give enough detail for a definite decision to be made.
The Ansuz and Tiwaz runes in particular seem to have had magical significance in the early (Elder Futhark) period. The Sigrdrífumál instruction of "name Tyr twice" is reminiscent of the double or triple "stacked Tyr" bindrunes found e.g. on Seeland-II-C or the Lindholm amulet in the aaaaaaaazzznnn-b- muttt, sequence, which besides stacked Tyr involves multiple repetition of Ansuz, but also triple occurrence of Algiz and Naudiz.