Sit down, gather round, listen to my tale
Of a time when humanity would finally fail
To conquer death like it always had,
we've died before, but this time was bad.
In threes they came, spreading like plague
We know many died, but the numbers are vague.
After many a year, the sick called "so long!",
Leaving only the lucky who managed to stay strong
Then I came I came along, and spirits were raised.
A new era was born, you'd be amazed
To live in my kingdom, when life was the best,
When the whole human race put their limits to the test.
Should be pretty easy... So what am I?