Moment's Peace is a common from Odyssey. It's a Fog with a Flashback: that's good.
My explanation for the coming spike is not very insightful. I think it's simple: hordes of new players have finall outstripped a very limited supply of a very good, old card.
Non-foils are headed from $0.50 to $2.00 in the coming weeks, and Foils are likely jumping from $5 to $15 over the same period. There will not be much of a slackening of price after the spike, unless Moment's Peace sees a reprint somewhere soon (Commander is a distinct possibility, but this was likely NOT in Wizards' reprint radar until... a couple weeks from now).