Metal Allegiance, the metal supergroup featuring core members David Ellefson (Megadeth), Alex Skolnick (Testament) and Mike Portnoy (The Winery Dogs, ex-Dream Theater), along with multiple special guests, have posted a new webisode for their song “Let Darkness Fall” featuring Troy Sanders (Mastodon) Randy Blythe (Lamb Of God), Mark Menghi and Rex Brown (Pantera, etc.). Check…