A dark essence block is an item created by using dense essence blocks on the Dark Altar located in the northern area of the Arceuus House in Great Kourend.
Creating dark essence blocks require 100% favour with the Arceuus House. You need a chisel and a pickaxe to obtain the dark essence blocks. Each dark essence block created gives the player 2.5 Runecrafting experience while draining 1 prayer point. They can still be made without any prayer points remaining.
It is used in the creation of Arceuus spellbook teleport tablets instead of soft clay. It can also be used with a chisel to turn them into dark essence fragments, which provide 4 essence pieces per dark essence block, which are required to runecraft blood runes and soul runes. Dark essence blocks disappear upon death.