It's fittingly called "Armageddon" and seriously is 65% alcohol (130 proof). To compare, vodka is usually 80 proof, rum around 93, wine about 25, and beer from 7-10 proof on average. It comes in a 330 mL bottle from Scottish brewery Brewmeister and apparently "has a lot of flavour - malty, hoppy, slightly sweet and lots of yeast". I doubt that, as it probably smells like rubbing alcohol with a hint of beer. To achieve the crazy alcohol content and still qualify as "World's Strongest" beer, the brewery actually froze the beer and removed the ice from the top, effectively concentrating the end product.
If you were wondering, drinking one bottle of Armageddon is equivalent to drinking almost 15 beers at 4% alcohol or a 12 pack of 5% beer. Wow.