Pre-Christian Slavic writing
Pre-Christian Slavic writing is a hypothesized writing system that may have been used by the Slavs prior to Christianization and the introduction of the Glagolitic and Cyrillic alphabets. No extant evidence of pre-Christian Slavic writing exists, but early Slavic forms of writing or proto-writing may have been mentioned in several early medieval sources.
Source: Wikipedia — Pre-Christian Slavic writing (CC BY-SA 4.0)