Strange symbols in TDD & AMFP

[Alardem]

It's the same reason why the sketches from Justine were reused in Mandus' secret passageways. :p They have different meanings in different context.

It's likely some occult nonsense, which thankfully none of the games expanded upon. From what I recall, it appears in the deeper sections of Brennenburg as a hint at how ancient the castle truly is. Also remember that it starts appearing around the time you meet Agrippa and learn of Weyer the sorcerer.

In Mandus' church, it's likely a sign that Oswald is turning to long-dead spiritual beliefs instead of Christianity. Stained glass depictions of Aztec sacrifices and crucified pigs don't belong in a church.