MOON RUNES: These are silvery, shining letters, drawn with the
finger on any reasonably solid surface. They may glow constantly, or
be “set” to shine under certain conditions, such as the presence of a
specific person, or a certain time of day. Likewise, they may also be set
to fade under certain circumstances, or after a preset length of time.
Duration: 1 year, maximum.
 
Dungeons & Dragons Dragon magazine - Spells The Dragon #18