Jim Berger wrote:

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Since you said both, here's a legend idea:

When the world of EdenAgain was young, the OverLord created
the first man and woman. Soon they anticipated their first child.
On the night their son was born the OverLord visited them in
physical form and it was a blessed event. The Creator of the
world gave the third moon the task of marking the event of the
new blood in the world by shining red for that night every year.

The first family named this night, the night of the first born son.
Years later under the influence of the Great Red Dragon the son's 
younger brother also chose this day to murder his brother out of 
jealousy of his specialness in being first born. When the OverLord
comforted the first man at his loss He told him "Fear not, you
will not be the last father to lose his son in the Great Conflict,
but all loses will be repayed in untold celebration one day."

Long after as the people of Talania turned from the OverLord
the evil forces twisted the meaning of the night of the first born son
making it the night where all children born must be given to the
dragons.

As to the physical explanations I leave that to the Learned 
Teachers of the Sciences of the OverLord (ok I just made that
up, don't try finding it anywhere!)

-Jim Berger 
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