Hidden Temple Altars are pieces of furniture that can be used for storage and display alike. It currently has 9 slots.
These storage containers can be crafted in your Crafting Menu (default key "q") after the according crafting recipe has been added to the crafting menu by buying it in the Store as a part of the "Hidden Temple Super Bundle". Just like all store-bought recipes it will also carry over to all other gameworlds that you'll be playing on.
To craft one Hidden Temple Altar, you'll need (as of R44 in June 2017)
- 2 Stone Slabs made of Stone, Limestone or Bedrock in a Processor
- 1 (block of) Wildwood, taken from Wildwood-trees found in Jungle biomes, which does not require any Power Cells to be equipped
- 1 (block of) Tourmaline mined from the Lava layer underground, which requires at least a Stone Mining Cell to be equipped, or obtained from Warmworms either as a loot or pet-harvest
- 1 (block of) Stone mined from Caves, Mountains, rocky hillsideds, recesses at rivers or the Fossil layer underground close to the surface, which currently does not require any Power Cells to be equipped
When buying the Hidden Temple Super Bundle, you will also receive a few blocks each of Tourmaline and Wildwood as additional gifts.
The Altar (despite its shape) is a 1-block-sized storage chest with 9 slots. It does not require any free space above to be opened. To use the Hidden Temple Altar for storage, you will have to place it into the game-world (by using the quickbar) and then activate it by right-click or typing "f" (as the default key) when looking at it.
You can put whole stacks of stackable materials/blocks/items into any of the 9 storage slots from your inventory or quick-bar by right-clicking or dragging & dropping with your left mouse-button. If you hold a stack of stuff with your mouse-button (left click), you can drag it over an empty slot and then right-click to drop only one piece of the stack (also repeatedly). You can also hold left shift + left click, then drag to move half a stack, or hold left shift + right click to move five items, or hold left ctrl + right click to move one item.
You can use the same kind of procedures to take stuff / stacks from storage slots into your inventory or your quickbar.
As with many storage items, you can name the Hidden Temple Altar individually (these names will be shown when you look at them instead of "Hidden Temple Altar") by activating/opening the Altar and then clicking on the icon that looks like a square (note) with a pen to the right of the word "Hidden Temple Altar". You can type up to 30 characters into this array. Even though while writing into this field all letters look like capital letters, lower case letters will be displayed just the way you wrote them after confirming your entry with "enter"/"return".
You can also change a few settings for each Hidden Temple Altar by clicking on the padlock icon shown in the top right corner after activating/opening the Hidden Temple Altar. Here you can set individual authorizations to control who can get access to this Hidden Temple Altar (and especially its contents). Available permission-settings currently (June 2017) are: "just me", "world owner/admins", "world mods", "builders" or "everyone". On Claims the available settings are "just me", "claim admins", "claim interact only", "claim builders" and "everyone".
These Hidden Temple Altars cannot be picked up as long as anything is stored inside. After emptying them, you can pull Hidden Temple Altars even without having any Power Cells equipped (since R32 in June 2016). Different from spawning Treasure Chests, you can actually receive and keep Hidden Temple Altars when picking them up, as they are furniture and such "real" storage containers.
You can rotate Hidden Temple Altars too by holding down "r" as the default key and dragging the object with your left mouse button, however only as long as they are empty (no items/materials/blocks stored inside). Currently, pieces of furniture except for Arctek ones cannot be found in the world nor can they be obtained from any creatures.
The "Hidden Temple Super Bundle" also includes crafted 2 Hidden Temple Altars in a single block kit that can only be claimed once on one Creativerse gameworld.