A crew of artists and outcasts haunt the Dragon’s Den. To find the second-story lounge, head down a narrow alley and up a rickety, twisting staircase. Inside, it looks a bit like an opium den. The entertainment, which is the real reason to come here, might be experimental noise, an ultra-cool DJ, or a troupe of belly dancers, and the audience is never more than a few feet from the stage. For a breath of smoke-free air, climb out onto the balcony above the crowds heading up the block to other Frenchmen Street clubs.