Rosarius

The definition of practical jewelry, a Rosarius is a small amulet, design-wise often in keeping with the Imperium's eagle fetish, that acts as both a symbol of authority for high ranking members of the Ecclesiarchy, and personal defence, as it projects a conversion field that converts would be lethal blows into flashy light shows. That last point is particularly important as it was used by Goge Vandire, The Universe's Most Evilly Named Man to trick the Brides of the Emperor into believing that he was protected by divine intervention, sparking that whole Reign of Blood thing, oops.

As the Imperium is an insular cliquey clusterfuck of a beurocratic organisation where no-one can play nice with one-another, the incredibly useful Rosarius is horded by the Eccles Cakes and only given out to those they deem zealous enough. So the next time you're sitting around wishing your squishie 'umie could have an invulnerable save, you know who to blame them for not being devout enough *BLAM!* HERESY!.

Notable Users

• Space Marine Chaplains are given one as part of their 'welcome to being a priest of the emperor' starter pack along with the fancy hitting stick and sent on their merry way. The Wolf Wolves get a Wolf Amulet for their Wolf Priests because their fenrisian torrets is getting out of hand and someone should really go check if they're okay.
• As the not quite military arm of the Adeptus Ministorum, SoB Canonesses get to keep their un-helmeted heads safe from rogue shrapnel without having to cut down on the manic street preaching during battle.
• Despite having very little special about them, Priests, Confessors and Missionaries get them for the same reason, I suppose the Ministorum wants to protect their investments as people that hopped up on the Imperial Truth are less common than ancient technology.
• Although the Inquisition on the whole in theory doesn't have access to them, some Inquisitors either have friends in the right places or put on a good enough show to get one, though this is more likely for Witch Hunters due to how close they work with the bffs of ecchlesiarcy. Sometimes a particularly brazen inquisitor might requisition one from the corpse of a fallen priest, and almost always having the highest say-so in the room, they might just get away with it.