Altars (synonyms: shrine; example toponyms: Altar of Atheus) are tables or platforms on which religious offerings or sacrifices can be placed. They can exist on their own or be a part of a crypt, temple, cult chamber, sacred grove, or other location. They may be present on holy islands, mountaintops, on ley lines, or near the mouth of a volcano. Typically altars are made from stone but other materials (wood, crystal, bone, etc) should be considered (this may be an opportunity for a fictional material). There may be religious symbols, icons, or runes carved onto the altar. Altars may be simple or ornate.

When designing altars for your fictional world, consider the religion or belief system to which they were built. Symbols or motifs important to these beliefs may be inherent to the altar. Also consider the types of offerings this altar was designed for – flowers, fruits, blood, animal sacrifice, human sacrifice, wine, prayer, or the burning of incense are some examples.