What does Marriage Prayer Brooch do in CK3?

Piety +0.2/month (patch 1.20.0.3).

How do you get Marriage Prayer Brooch with the console?

effect generate_romantic_trinket_effect = { OWNER = root } — runs the scripted effect that makes it, for the character you play (debug mode).

Personal artifact · Trinket

Marriage Prayer Brooch

MasterworkTours and Tournaments

Marriage Prayer Brooch is a masterwork trinket artifact in Crusader Kings III: Piety +0.2/month. Quality 35 and wealth 35; maximum durability 75. It needs Tours and Tournaments. Patch 1.20.0.3, from game/common/scripted_effects/02_ep2_artifact_effects.txt.

Quick answers (2)

What does Marriage Prayer Brooch do in CK3?: Piety +0.2/month (patch 1.20.0.3).
How do you get Marriage Prayer Brooch with the console?: effect generate_romantic_trinket_effect = { OWNER = root } — runs the scripted effect that makes it, for the character you play (debug mode).

An annular, flat brooch, engraved with a marriage prayer, enameled.

Effects

Piety+0.2/month

How it is made

The game creates it with the scripted effect generate_romantic_trinket_effect. In the console (how to open it), this gives it to the character you play:

effect generate_romantic_trinket_effect = { OWNER = root }

Built from the effect's file; not run in the game by us.

Source: game/common/scripted_effects/02_ep2_artifact_effects.txt, common/modifiers (artifact_monthly_piety_2_modifier) and the English localisation, Crusader Kings III 1.20.0.3.