The Maulerfiend is the signature engine and the only unit that can take Talons of Butchery. Its Scent of Blood ability was rewritten in this pack: +1 to charge rolls near an enemy unit below starting strength within 9 inches, or +2 near one below half strength.
The Defiler is the datasheet this pack reprints in full on page 5, making it the best-evidenced unit in the detachment: 14 inch move, Toughness 11, 18 wounds, a 5+ invulnerable save, and Scuttling Walker, which lets it move through models and terrain and automatically pass Desperate Escape tests.
The Helbrute is the cheaper body, and its Frenzy ability was rewritten in this pack so that once per turn, when an enemy targets it in the Fight phase, it becomes eligible to fight again and must be selected to fight next.
We link no boxes for any of these three because our catalog holds no exact entries for them, and pointing you at an approximate kit would be worse than pointing you at none.