In DAEMON, each spirit you summon will have its own unique seal. A "genuine" seal from the Ars Goetia is given below:
I've written code to procedurally generate similar-looking seals, given names and colours which as passed in as parameters:
Rendered on screen using Libtcod's functions the above seal appears as (actual size):
What's the point of all this? None actually, from a strictly game-play point of view, but I think it increases the atmosphere quite a lot.