Angelic Runes

Because Angels have a long standing and ever-eternal policy of not interfering, the only true angels you can communicate with are the fallen - Demons. And you do not really want to associate with those, unless you are in it for the dark magic itself. Through centuries long study of theology and other celestial aspect, people started assigning (or discovering) names of the truly holy and bright ones, with complicated and intricate sigils that have been used in church architecture and iconography. While the angels themselves would never do anything that would go against their God (unless they have fallen victim to corruption like their fallen comrades), clairvoyants and several other magically endowed folk can peak into the secret and most sacred realms there are.
Thanks to all this, the collection of angelic runes, a special kind of religious alphabet, has been developed over the centuries. While it cannot be used as a language on its own, religious officials, artists and cults use them as a way to communicate their intentions and agendas to other people in the know - while keeping it secret from the public. However, even though this "alphabet" cannot be used in direct communication with the Angels themselves (like the demonic names can be used to call on the infernals), people still believe that using specific runes in specific places can invoke their influence or at the very least gain a minor blessing or simply - some of that luck. Others (mostly common people and not religious officials) see it as a way of adoration - prayer tokens with angelic runes are seen as a way to show one's devotion to not only God, the highest authority ever, but also to other things created by them - even those unseen and unheard and uncomprehensible. Everything and everyone deserves a bit of love and respect, and so do Angels.