I'm still wrapping my head around this, but that Spellbreaker Song scares me. If the bard pumps their cha mod up to +10, it basically becomes "spend one bardic music to turn all primary spellcasters you don't like into squishy commoners for 10 rounds. No save."

While I can appreciate the intent, there's gotta be some better way to scale that. 10-20% spell failure might make no difference at all in a battle. 50-60% spell failure might let some mid-level chumps crush Xykon.