Utrecht Psalter.
The Utrecht Psalter is an illuminated manuscript from the 9th century that’s famous for its rich palette of motifs, illustrations of the psalms and canticles, revolutionary dynamic style, and visual messages about proper rulership. The illustrations reflect the violence and warfare of the time but are meant for moral instruction, apparently for a (future) king, and known as the first visual “mirror of princes.” Its production was a defining moment in Carolingian culture and forms a crucial link between Late Roman art and its Carolingian translation. It’s a key manuscript of Christian art and no other illuminated manuscript has exercised such a profound artistic influence and legacy.