What does Stone of the Western Wall do in CK3?

Prestige +0.01/month (patch 1.20.0.3).

What if the owner can't benefit from Stone of the Western Wall?

They get Court grandeur baseline +3 instead.

Court artifact · Pedestal Item

Stone of the Western Wall

IllustriousUniqueHoly relic

Stone of the Western Wall is an illustrious pedestal item artifact in Crusader Kings III: Prestige +0.01/month. Quality 100 and wealth 100; maximum durability 150. Patch 1.20.0.3, from game/common/scripted_effects/02_starting_holy_site_relics_effects.txt.

Quick answers (2)

What does Stone of the Western Wall do in CK3?: Prestige +0.01/month (patch 1.20.0.3).
What if the owner can't benefit from Stone of the Western Wall?: They get Court grandeur baseline +3 instead.

A worked stone drawn from the western retaining wall of the Second Temple's platform, one of the few remnants left standing after the Roman destruction of the Temple in 70 CE.

Effects

Prestige+0.01/month

For an owner who can't benefit from it

The template gives these instead of the effects above when its “can benefit” check fails:

Court grandeur baseline+3

Who can benefit (can_benefit) (1 line of game script)

jewish_artifact_access_trigger = yes

As written in game/common/artifacts/templates (judaism_relic_template).

Counts as a holy relic for (is_holy_relic) (6 lines of game script)

OR = {
	religion = religion:judaism_religion
	main_rite = {
		rite_has_parameter = jewish_syncretic_actor
	}
}

As written in game/common/artifacts/templates (judaism_relic_template).

History and who has it

Made before recorded history.

How it is made

Made only inside events; no scripted effect to call from the console.

Source: game/common/scripted_effects/02_starting_holy_site_relics_effects.txt, common/modifiers (artifact_placeholder_modifier), common/artifacts/templates (judaism_relic_template) and the English localisation, Crusader Kings III 1.20.0.3.