Although the song refers to God (Dio) it is actually talking about Satan / Devil. That is the dark God ("Il nostro dio scuro").
As @DassJennir comments it is about worshiping and praising the dark God. I assume the reference in the song and title to "With Nails" (con clavi) is in reference to the crucifixion of Jesus and the nails driven through his hands/wrists. Or could it perhaps be in regards to nail in the coffin? That is in death they will join their God in the underworld.
Although the song refers to God (Dio) it is actually talking about Satan / Devil. That is the dark God ("Il nostro dio scuro").
As @DassJennir comments it is about worshiping and praising the dark God. I assume the reference in the song and title to "With Nails" (con clavi) is in reference to the crucifixion of Jesus and the nails driven through his hands/wrists. Or could it perhaps be in regards to nail in the coffin? That is in death they will join their God in the underworld.