Despite his moniker, as well as his choice in garb, the Rainbow Mage is an individual who may have been the most suited for an era of constant battle. While many mages are seen using their staves as long walking sticks, his is a shillelagh. And while a shillelagh can still be used as a walking stick, his is too comically large to be anything other than a blunt instrument.
His powers are "prisming," where he can separate the elements of anything he comes into contact with by pulling their strands of light apart in each swing. He can also hit really, really hard. He lost his eye in a duel between him and another Mage, something the Tower Wizard was very displeased with but ultimately had to respect. The Rainbow Mage replaced it with a relic that he carved down into a sphere, which allows him to see the magical strands flowing around him, and individuals.