A.D. Amorosi The power of Nick Cave had forever hinged on summoning the spirits of the dark.Be it his time as frantic frontman to the clamorous Birthday Party, or since the 1984 start of a menacing solo career with the floating membership of the Bad Seeds by his side, Cave’s catalog of violence-driven characters and furiously dire narratives cut like a knife, fresh with blood and amped-up with post-punk gospel fervor.That all of this changed in 2015, with the tragic accidental death of Cave’s 15-year-old son, Arthur, exemplified “the crack in everything” that Leonard Cohen, a noted inspiration to Cave, wrote of on “Anthem”: “That’s how the light gets in.”From Cave’s family tragedy, a second family emerged: that of a devoted fan base who showered the singer and author with warmth and comfort beyond fandom.