Complex sentence: They usally carry a massive, rusted blade known as a Plague Sword into battle, said to be dipped in the foul pus and contagion at the base of Nurgles throne.
Split into simpler sentences: They usally carry a blade known as a Plague Sword into battle. These massive, rusted blades are said to be dipped in the foul pus and contagion at the base of Nurgles throne.