But once upon a time, there was a huge battle between priests loyal to the god Numiel, defending a town under their protection, against a huge band of marauding cyclopes.
Things looked grim for the defenders; the cyclopes came close to victory.
But then a flock of passing peacocks, who had a preëxisting grudge against the cyclopes (who were in the habit of raiding nests, not for food, but to smash the eggs out of pure malice), joined in, and turned the tide of battle.
The defenders defeated and drove off the cyclopes, and the town was saved.
As penalty for their wicked ways, Numiel struck all but one eye from each cyclops. As a reward for their assistance, he bestowed all the eyes upon the peacocks, instead.
This is why cyclopes only have one eye, why peacocks have many extra eyes on their tails, and why peacocks are among the creatures sacred to Numiel.
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What prompted this revelation? Well, it all has to do with the Reaper Bones kickstarter. (I was one of the silly few who didn't spend the whole $100, because I knew I wouldn't have the patience or sticktoitiveness to paint all hundred gazillion minis. Instead, I spent somewhat less, for a much worse value. Oh well!)
In particular, it has to do with this guy. (No human being can paint that intricately. Their examples are obviously painted by unseelie creatures of fey.) I took one look at him, and decided he's a paladin. And, of course, in my world, paladin means Numiel. (Even though Sequoia, Urmaggr, and Dalya are also compatible with paladinhood.)But what's that on the back? A peacock? ...obviously, since this is a paladin of Numiel, peacocks must be sacred to Numiel. Done. But why? And so a little story struck me. So here you go.
And the moral of the story is: no matter how little and silly and nonsensical an idea might seem, add it to your campaign setting as soon as it strikes you. Campaign settings often seem generic and boring and soulless, and seemingly incongruous little details like this are a good way to combat that tendency.