The Rune of Self Sacrifice increases the amount of Life Essence gained in the Blood Altar through means that use a player's health. Each rune gives a bonus of +10% additively per rune.
With some Netherite Scrap and some Intricate Hellforged Parts looted from the Demon Realm, you can double the power of your Rune of Self Sacrifice, increasing bonus to an additive +20% per rune.
If you change your mind, you can undo the recipe in the ARC.