Anthem is an entity that surpasses comprehension. Ancient beyond reason, Anthem seems to be A being of patterns and sequence. The Cadence is not defined by substance, but rather the forces that travel through it, impacts, vibrations, and sound. It is the pattern of these things that give Anthem power and being.
Like others of its kind, the entity is unavoidably entwined with the world. Its very presence taints all things that touch upon its concerns, however it is unable to act directly upon the physical realm without immense focus. Individuals with a strong affinity for sound and rhythm may draw its attention through maintaining such patterns at length, but even these instances are not a certainty of its attention.
Places where anthem focuses its presence fall naturally into patterns of movement and sound. It gathers near the sea, in whistling caves, and the depths of forests - anywhere patterns of movement emerge. Without the intervention of a guiding voice, these patterns tend to become surreal and sometimes discordant. Those enthralled by Anthem act as shepherds for these locales, creating harmony and reinforcing the entities grip on the world.
A being in the presence of Anthem gains advantage on all rolls so long as it maintains rhythm and pattern with its actions and sounds. Creatures who resist or ignore the rhythm suffer disadvantage on all rolls while in the area.