How do you get Eight-fold Chest with the console?

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

What if the owner can't benefit from Eight-fold Chest?

They get Court grandeur baseline +3 instead.

Court artifact · Pedestal Item

Eight-fold Chest

IllustriousUniqueHoly relicAll Under Heaven

Eight-fold Chest is an illustrious pedestal item artifact in Crusader Kings III: Court grandeur baseline +6, Domain Taxes (Same Faith) +15%, Piety +0.3/month, Buddhist Opinion +5. Quality 100 and wealth 100; maximum durability 150. At game start it goes to the holder of China — needs All Under Heaven. It needs All Under Heaven. Patch 1.20.0.3, from game/common/scripted_effects/01_exp1_historical_artifacts_creation_effect.txt.

Quick answers (3)

What does Eight-fold Chest do in CK3?: Court grandeur baseline +6, Domain Taxes (Same Faith) +15%, Piety +0.3/month, Buddhist Opinion +5 (patch 1.20.0.3).
How do you get Eight-fold Chest with the console?: effect create_artifact_eight_fold_chest_effect = { OWNER = root } — runs the scripted effect that makes it, for the character you play (debug mode).
What if the owner can't benefit from Eight-fold Chest?: They get Court grandeur baseline +3 instead.

This is a set of eight small chests, each inside the other, with the relic of Buddha's Fingerbone placed in the central chest. The relic has been in use in welcoming ceremonies under successive Tang Emperors before these chests were made at the order of Emperor Yizong. Each chest is intricatly made in sandalwood, silver, gold and jade. The last chest is a four door pagoda in pure gold, housing the finger itself. The top of the pagoda is a lotus flower holding a golden pearl.

Effects

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)

has_religion = religion:buddhism_religion

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

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

OR = {
	religion = religion:buddhism_religion
	main_rite = {
		rite_has_parameter = eastern_syncretic_actor
	}
}

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

History and who has it

Made before recorded history.
Kept with the title China from 650.1.1.
At game start: the holder of China — needs All Under Heaven.

How it is made

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

effect create_artifact_eight_fold_chest_effect = { OWNER = root }

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

Source: game/common/scripted_effects/01_exp1_historical_artifacts_creation_effect.txt, common/modifiers (eight_fold_chest_modifier), common/artifacts/templates (buddhism_relic_template) and the English localisation, Crusader Kings III 1.20.0.3.