Sigil

The Sigils are triangular pieces of red and gold metal - ancient objects of power - each engraved on their front face with arcane symbols representing the seven Demons of the Pit (Grigori). They are keys entrusted to the Grigori which will open the Seven Seals at the time of Armageddon.

They are collected within the Codex. When a certain amount are found, they reveal another verse of the Litany, unlocking the corresponding Recreant Vault. Mike/Shadow Man must recover the Sigils, so that he might open the Seals and destroy Asmodeus.

(from Shadow Man 2econd Coming Game Scriptment)

Sigils needed to open each Recreant Vault are as follows:

Louisiana - 3 Sigils (+3)
Tarkovskaya: Russia - 6 Sigils (+3)
Moytura Island, County Clare: Ireland - 12 Sigils (+6)
Isle of the Dead: Deadside - 24 Sigils (+12)
The Pit: Gehenna - 36 Sigils (+12)