As mentioned, Megadeth are playing the Epiphone Revolver Music Awards at Webster Hall on Tuesday (12/13), which frontman Dave Mustaine is also hosting. You may remember Mustaine promoted the awards by bartending at Greenpoint's Saint Vitus. The venue just put up the above image on their instragram which seems to suggest that Megadeth is playing Saint Vitus on Monday (12/12).

The evidence: 1) Vic Rattlehead is the name of Megadeth's mascot; 2) "A Toute Le Monde" is both a Megadeth song and the name of their beer. We are not for sure but here is what Saint Vitus wrote about getting tickets:

So these are the rules to get tickets so pay attention!
1. Only them. No openers
2. Tickets will be available for purchase AT THE BAR ONLY on Thursday 12/8 and Friday 12/9 from 6-8PM, and Saturday 12/10 from 2-4PM, selling 60 tickets each day.
3. Tickets are $50 and cash only. Tickets will be all will call and non transferable. First-come, first-served. Again, we are only selling 60 tickets each day so when they're gone, we're done!

A little more info is at the mystery show's Facebook event page. Good luck.