The Soul altar may be found to the north-east of the Arceuus Library in Great Kourend.
According to the transvergence theory and soul journey, the soul altar located in Arceuus is not the real soul altar; this altar was created by the power from the Dark Altar located near it, where it drew energy from the plane where the real soul altar is located.
It is used to craft soul runes from dark essence fragments, providing 29.7 Runecraft experience. In order to craft soul runes, players need 90 Runecraft and 100% Arceuus favour.
Unlike most altars, the soul altar does not need to be entered. As such, neither a talisman nor tiara is needed.
It is possible to access the soul altar via the Abyss; however, the player must use a dark essence block or dark essence fragments on the rift after having crafted some soul runes first. This only has to be done once.
The maximum limit for crafting soul runes in one visit is 212. This would be achieved by mining 27 dense essence blocks and then turned into dark essence blocks and crushed with a chisel into dark essence fragments. Then, another inventory of 26 dense essence blocks are mined and turned into dark essence fragments before going to the soul altar.
Note that you can only have a maximum of 108 dark essence fragments and therefore must be used before crushing the remaining dark essence blocks. One dark essence block is equivalent to four essence pieces.
The maximum possible experience is 6,296 obtained while doing the above.
The soul altar north of Arceuus.
Pre-release view of the soul altar and its surroundings