TL;DR
AoE howl that damages all enemies, reducing their Haste and defense while dealing bonus max-health-based damage.
Dreary Ball bellows forcefully and inflicts beast damage of 280% Attack Rating on all enemies.
Lv 6 Beast damage dealt is increased to 300% of Dreary Ball's Attack Rating.
Lv 12 Enemies that are damaged become dispirited and have their Haste reduced by 20 points and Defense reduced by 20%, up to 40% of Dreary Ball's Defense, for 6 seconds.
Lv 18 Gloomy Howl causes additional damage equal to 5% of the target's max health, without exceeding 5% of Dreary Ball's max health.