This article has been verified for the current version (1.4) of the game.
The reliquary interface
Sacred treasures are artifacts of particular cultural, religious, or historical importance that can be placed in holy sites to provide a small modifier to every territory in the province. Each treasure is unique and there are only a finite number of possible treasures in the game, with most being placed at start and a few created through special missions or events, but can be collected and taken from other countries by desecrating their holy sites or seizing their reliquaries.
Each holy site has a certain number of altars, depending on the status of the territory it is located in: one for settlements, two for cities, and three for metropolises. Each altar is a slot where a treasure can be potentially placed, which will allow the treasure to be confer its bonuses to the entire province (not just the territory its holy site is in); it is therefore useful to build many holy sites and bring as many sacred treasures as possible to the capital province in order to maximize the effects of their bonuses. The treasures stored in each owned holy site as well as those of deities in the pantheon (even if unowned) can be viewed in the religion screen, while the presence of treasures in other holy sites can be inferred by looking for modifiers in the tooltip of the holy site icon in the territory interface.
A treasure can only be placed in an altar if its holy site's deity is in the country's current pantheon, though treasures that have already been placed will continue to give their bonuses to its province. There are no restrictions on where a treasure can be placed or when it will give its bonuses; any treasure can be placed in any holy site regardless of its religion or the state religion of the country that owns it. Treasures can also be removed from altars where the holy site's deity is in the pantheon and deposited back into the reliquary at a cost of +1.00 Aggressive Expansion, which leaves the holy site intact and the altar slot free for another treasure to be placed.
Treasures will also be removed from an altar if its holy site is destroyed through desecration. Desecration can be done through the Religion menu if the holy site is owned or by using the Desecrate Holy Sites army interaction on an army located in the holy site's territory. Importantly, the Desecration army action only requires that the territory is controlled, not necessarily owned, which makes it the easiest way to seize treasures held in the holy sites of other countries.
Unplaced sacred treasures are held in the nation's reliquary and confer no benefits, but cannot be taken through desecration. Treasures in the reliquary can be placed in owned holy sites of any deity in the pantheon, as long as there are altar slots remaining. Upon annexation by conquest, up to 2 treasures in the nation's reliquary will be spirited away to another country within diplomatic range if any exist, and all the rest will be taken by the conqueror. Diplomatic annexation, however, will transfer all reliquary treasures to the overlord.
Clicking on the reliquary icon in the religion screen will show a list of all the treasures owned by the country, including both those placed in all holy sites as well as those stored in the reliquary (identifiable as currently generically in the country as opposed to a specific territory).
Treasures are listed by the religion they are associated with, usually the deity of their holy site if placed in one or the state religion of the country that holds them in its reliquary. Note that this should not be taken as an indication that a treasure is tied to any given religion; any treasure can be installed in a holy site of any deity or religion and will always confer its bonus regardless of the state religion of the holy site's owner. Some treasures will also only appear if a certain DLC is enabled.
The ancient wooden xoanon of Troy, in the image of Pallas, was looted by Diomedes and Odysseus in the siege. It is rumored to have eventually found its way to Rome in the hands of Aeneas, where it is kept in the Temple of Vesta.
The carved wooden xoanon of Athena Polias is an ancient relic from the earliest days of Athens, housed in the Acropolis' Erectheion. It is said to have fallen from heaven and is regarded as the very holiest image of the goddess.
This stone is said to mark the world's navel, or center point, placed at Delphi by Zeus where two eagles sent from each end of the world met. It also represents the swaddled stone Rhea gave to Cronus to protect the infant Zeus.
The two sacred Manalis Stones differ in their purpose but share a name. One of the stones is used to block the entrance to the underworld (Mundus Cereris), while the other is associated with the coming of rain.
The Crowns of Upper and Lower Egypt have been the symbol of royal rule along the Nile for millenia. This crown in particular was most recently worn by the Greek Pharaohs of Egypt, but similar crowns have been in use since the 18th dynasty.
The divine, pyramid shaped, Benben stone, represents the primeval hill upon which Atum first landed. For centuries it was kept in the very center of the Ra temple at Heliopolis. This stone serves as a model for all Pyramidion's and the tips of Egyptian Obelisks.
Stelae are monuments seen across the Carthaginian world, simply as an offering to a deity or as a grave stone and offering both. Dedications to Ba'al Hammon, as one of the two most important deities in Carthage, were often a popular choice to carve into the stone.
This idol is one of a pair of idols, of the two deities Ga and Gacim. It is said the two were fertility deities and fate-spinners, and both idols have been the focus of religious cults. The impressive silver idol has become noteworthy for its great artistry far beyond our borders.
This idol is one of a pair of idols, of the two deities Ga and Gacim. It is said the two were fertility deities and fate-spinners, and both idols have been the focus of religious cults. The beautiful gold idol is worth a fortune in its own right.
The walls of Babylon are adorned by a great processional gate in glazed blue, yellow and brown bricks. Built as a homage to Ishtar and the Babylonian gods by Nebuchadnezzar, the Ishtar Gate and the walls of Babylon are considered one of the seven wonders of the world by many.
The polychrome statue is of a seated matriarch, made in the ancient past of Iberia. It is unclear if the statue is of a local deity that has disappeared since its creation, or a local matriarch of some importance.
This carving was once part of the palaces at Persepolis and depicts the struggle of the hero King Sharhriar against a supernatural winged lion. 'Ahuramazda helped me to defeat this land and restore order to him'
The origin of this Black stone is unknown but it has been worshipped in the Kaaba in Arabia for longer than anyone can remember. Some say that it once fell from the sky and it has often been associated with fertility rituals.
Purported to hail from the far off island of Hibernia, the legend surrounding this chain-mail suggests that the king who bore it, held invaders at bay for over a year, whilst barricaded inside his hill fort.