A "quadrupel" is an Abbey-style ale whose name has no real significance other than to indicate that, well, it’s stronger and more complex than a dubbel or a trippel. Portland’s Allagash Brewery, one of the nation’s finest purveyors of Belgian-type beers, has been brewing the delectable Dubbel Reserve (seven percent ABV), dark red-brown and smacking of chocolate and anise, and terrific Trippel Reserve (nine percent), luminous gold and bursting with fruit and herbal notes, for years now. But in the new Allagash Four, the brewers have outdone themselves.

Made with four malts (two-row, Munich, and two kinds of caramel), four hops (Perle, Hallertauer, Tettnanger, Saaz), four sugars (date sugar, golden molasses, light-colored candi, dark-colored candi), and fermented no fewer than four times with four different kinds of yeast, Allagash Four is a monster — but a benevolent one.

Those four fermentations yield a beer that’s deeply complex and compulsively drinkable. It pours heady and robust, with only the faintest trace of light managing to penetrate the murky depths of its slightly cloudy, deep crimson-earth color. It’s all capped by a dense, meringue-like head.

The potent tang takes a moment to register. But when it does, it makes itself noticed. The spice character is quite strong but exquisitely balanced: cinnamon, clove, black pepper, a bit of allspice. It lingers long, losing little of its intensity, with sweetish sapors of raisins and toffee appearing subtly as it fades.

Apparently, "Allagash Four" was a term in circulation before this beer was conceived, referring to a quartet of hapless campers in the Northern Maine wilds who were abducted by aliens in 1976. The flavors at work here are just as dark and mysterious, and just as transporting, as any interplanetary craft.

Available for $9.95 for a 750-ml bottle at Downtown Wine & Spirits, 225 Elm Street, in Somerville. Call (617) 625-7777.