Altars are objects found in the Underworld. Interacting with one can produce positive or negative effects:
- Your hunger bar can be emptied.
- Your health and hunger bars can be filled.
- The altar can spawn any random monster in the game.
- The altar can double one stackable item in your inventory* (restrictions apply).
- The altar can do nothing.
- The altar can disappear.
The number of uses an altar has is also random.
The altar can randomly select a stackable item in your inventory, and dupicate it.
- This process will add up to 30 of the randomly selected item to your inventory.
- Steel bars, healing potions, and silver have a cap of 10 instead of 30.
- You can only gain 2 gold from an altar, and if you have more than 10 half will vanish!
To leverage this mechanic you can drop any stackable items in your inventory besides the one you wish to duplicate before interacting with the altar (putting a floor tile down first is a good precaution). Just do not drop gold facing the altar if you have infamy, unless you wish to remove it.
If you have infamy, dropping gold while facing an altar will pay to remove some of it.
This mysterious structure is more common in the deeper parts of the underworld, and its inner mechanisms are fairly complex. When you combine two items the dominant item will attempt to absorb better traits from the lesser item. The dominant item is usually determined by level requirement, unless one of the items is custom (smithed or named), in which case that will be the preferred item. Equipment can be named on these altars just like on anvils.
You can offer gold to the altar to boost its power, though it is optional. This increases the chance of upgrading traits, and reduces the chance of the altar disappearing after use. Items of a similar power level (or even better the same type) have better results when melding. Gem bonus slots have a chance to transfer completely, and will not upgrade or downgrade.
Runes behave differently, they upgrade by 1 until maxed out if the absorbed item has the same or a higher level rune. Higher levels will have a greater pull and have better results. Similarly runes can downgrade if they are mixed with inferior runed items, but the chance of upgrading is always higher than downgrading. A fully powered glowing altar will guarantee at least one rune upgrade if it is available. If the items are of the same type then even natural plus bonuses (+1/2/3) can be absorbed.