Even the baddest-ass metal bands usually have some disarming, cartoonish quality about them. Black Sabbath seems like a group of harmless drunkles at a family reunion. Judas Priest has Rob Halford, who dresses like Tom of Finland and whips motorcycles. Even those murderous Black Metal bands from North Drinkingland are rendered less menacing by all that silly corpse paint and those medieval-weapon props. But not Slayer. Admittedly, Slayer started out with a cuddlier name, Dragonslayer, and wore football eye-black in the early days, but those goofy elements were ancient history by the time the band achieved any sort of evil prominence. Slayer was just pure unadulterated devilry: no smirking, no songs about girls, no gimmick. Until now. The band is currently on tour performing its classic work of thrash, Reign in Blood, in its entirety. The surprising bit is that the climactic song, “Raining Blood,” is now accompanied by a Gallagheresque gambit that involves the band’s being drenched in fake blood. This is achieved with some perforated tubing and gallons of red dye. Though it is officially called the Wall of Blood, the effect comes off more like the Irrigation System of the Damned. The intent surely was to make Slayer look even more diabolical, but the fact that they have had to resort to gory precipitation actually makes ’em seem kinda cute. It is unclear whether pentagram-imprinted plastic ponchos will be for sale when Slayer plays with Killswitch Engage and Mastodon at 6 p.m. Tuesday, Nov. 23, at Nation, 1015 Half St. SE. $35. (202) 397-7328. (David Dunlap Jr.)