My source is borne upon the wing of valkyries of gold,
They work their magic summer long then winter through the cold,
Once the black and golds are done I'm plucked with careful hand,
And left to swim among the shrooms until it's time to stand,
And in that time my power grows as was the hand's intent,
Til even mighty fall like fools when my power is spent,
Though fewer know me by the days, some think I'm in the past,
My history is far from gone, it stretches wide and vast.
What am I?