The Blood altar is used to craft blood runes from dark essence fragments, providing 23.8 Runecraft experience. It may be found to the east of the Arceuus Library on Great Kourend.
In order to craft blood runes, players need 77 Runecraft and 100% Arceuus favour.
According to the transvergence theory and soul journey, the blood altar located in Arceuus is not the real blood 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 blood altar is located.
The location of the Blood altar.
Unlike most altars, the Blood altar does not need to be entered. As such, neither a talisman nor tiara is needed.
In order to access the blood altar via the Abyss, the player must use a dark essence block on the rift after having crafted some blood runes first. This does not consume the dark essence block, and only has to be done once.
The maximum limit for crafting blood 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 blood altar.
This limit can be increased to 232 with the completion of the elite Kourend & Kebos Diary, which awards an extra 10% of blood runes per bind. However, no additional experience is gained.
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 5,045.6 obtained while doing the above, but each subsequent inventory will be 4,855.2 experience due to the blood runes taking up an additional inventory space.