as for custom magic: my wizard is toying around with various means of communication possibilites, seems to be a hobby of his.
he did a "homing pigeon" spell, where a spell construct pigeon carries the messages to his allies. makes only sense if in the same city or it might take to long.
just as I was writing this, I am thinking of some sort of magical "mail" or "forum" gadget. say you have three people who want to communicate and have them participate in a ritual that enchants a large (but empty) book, and dedicates it to them. after the rite the book is divided between the three. the magic could work like this: the individual parts of the book "remember" being part of a large thing and everything written in it can be seen by a person holding one of the other parts, making it something like a web forum, just without the internet. just an idea i an toying around in my head.
