The Signum

[AllenCecil]

Exactly what is it? The Inventory portrays it as a sort of symbolic badge that grants damage & suppression skills to the weapon. It appears to be an Inquisitorial lore artifact, but precisely where is it placed in relation to the weapon? While I'm at it, the same with the Purity Seed, which also seems to be an artifact, where also is it placed in relation to the body armor?

[Grim@FU_BARRACUDA]

all ik is that in the game (space hulk deathwing) wich is also a wh40k game you can put signum like stuff on the side of your weapons

but they have no effect its more a status symbol that shows your place or earnings in the chapters hierarchie

sure some of them are relics given for one to another over time and some may have "powers"

you may find something here about it here: https://wh40k.lexicanum.com/wiki/Main_Page

[Irrelevant]

Well people in 40k get decorated with seals and stuff like that. You see those mostly on armor Just a stamp with a pice of written paper (or whatever) underneath. A Signum is the same thig just put on weapons.
They have no impact whatsoever they mostly just push the owners morale because humis are no Orcs... no faster running in red armor or whatever the orc colour code offers ^^.

It's just fluff and it's used for another Item slot in Martyr.

[Tacitus]

Purity seals are wax seals affixing strips of parchment with prayers on them. It's basically a declaration that "I'm Chaos free!" The idea of fixing strips of parchment with wax seals is an ancient one in the Imperium, dating back to the Great Crusade with the Oaths of the Moment that Astartes would swear before going into battle. However, I suspect that the idea of having prayers on these seals may have originated with the Word Bearers. Although when they turned to Chaos, they started printing their purity seals on less appealing materials like human skin...

Irrelevant is right that they slap them mostly on armour, but they can put them on just about anything that they deem worthy of blessing--artillery pieces, aircraft, or in the case of the Adeptus Mechanicus, machinery, doors, or toasters.

As for the Signum, it's just a devotional badge. It don't think it's supposed to be the Inquisitorial rosette that all Inquisitors would have. If you look up "signum" on Lexicanum, you'll find a different description for a communication device used by the Deathwatch. The signa (pl.) that the characters in this game can wear aren't communication devices.

Edit: I guess the in-game plural used is "signums," but the Latin "signa" comes a bit more naturally to me!