É mencionado novamente brevemente no livro 20 "The Primarchs" no início do conto "O Leão".
O Leão El'Johnson parece muito menos confiante do que antes e é mencionado:
Trust had been a scarce commodity for the Lion before Horus's betrayal and even then he had been taken for a fool. Perturabo had used his status as a brother to trick the Lion, taking control of the devastating war engines of Diamat under the guise of alliance, only to turn those weapons against the servants of the Emperor. The shame of being so manipulated gnawed at the Lion's conscience and he would never again accept the simple word of his brothers.