So we're still doing this thing where we crowdsource campaign material...
The Lottery in Babylon
Like all men in Babylon I have been a proconsul; like all, a slave; I have also known omnipotence, opprobrium, jail. Look: the index finger of my right hand is missing. Look again: through this rent in my cape you can see a ruddy tatoo on my belly. It is the second symbol, Beth. This letter, on nights of full moon, gives me power over men whose mark is Ghimel; but it also subordinates me to those marked Aleph, who on moonless nights owe obedience to those marked Ghimel. In a cellar at dawn, I have severed the jugular vein of sacred bulls against a black rock. During one lunar year, I have been declared invisible: I shrieked and was not heard, I stole my bread and was not decapitated.
-- from Jorge Luis Borges, The Lottery in Babylon(translation by I actually don't know)
The Babylonian Library still exists, though now it is practiced mostly by jackal-headed men who live beneath the earth.
All who would pass through the doors that stand at the entrance to the territories of jackalmen must first draw a fragment of carved bone from a Well of Fate.
Each bone marks s/he who drew it with a symbol (on the forehead, usually, if the creature has one), and the faith of the jackalmen demands that all jackalmen obey the mark until it fades (usually after one day), treating each visitor as the mark demands, no matter how s/he behaves.
The bond is not magical (though the forces that keep the doors of the realm from opening for any traveller who does not bear a mark and the forces which cause the mark to appear on the bearers skin are) and the jackalmen obey these marks in obedience to sacred custom, rather than mystic compulsion. The marks never literally grant the bearer abilities or compel them to commit acts.
The marks are:
1. The bearer of this mark must be ignored.
2. The bearer of this mark must be given fresh meat three times. (The bearer may be slain, but must be fed first).