Is it

>! Mead

"My source is borne upon the wing of valkyries of gold,

They work their magic summer long then winter through the cold,"

>! Bees make honey

"Once the black and golds are done I'm plucked with careful hand,"

>! Honey collected by beekeepers

"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,"

>! The honey is left to ferment into mead

"Til even mighty fall like fools when my power is spent,"

>! Mead gets people drunk

"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."

>! Mead was more popular historically than in the modern age