Cylun

Go to the pause menu and select solomon's key. Then, go to a specific area on the map. You place crests on certain locations. Guided by the hints, you should be able to place all the crests in the right position and upgrade the crests. When upgraded, crests gain an extra spell that is quite usefull, some extra spells make seamingly useless crests useful, others make good crests better(asmodeus gains bright crest, for example), and some give you lovely abilities(arc gale, gathering, raise up, etc.)