Sacrifice was originally purchasable during the second world event with 21,000 renown and a gold event token. With the world event being over it is now obtainable through other methods. It can be obtained as a very rare drop from General Graardor and Kree'arra.
You can also obtain Sacrifice, as well as the Devotion and the Transfigure ability easily through killing the followers of Armadyl and Bandos in their respective encampments in the God Wars Dungeon, such as Aviansies. To obtain the abilities Lootshare must be Enabled. These abilities are individual drops, however you may receive multiple abilities in a single kill.
When received as a drop from either the Generals or the followers, it is automatically learned; it does not drop as an item. When received as a drop, the message "You have unlocked the Sacrifice ability!" appears in the chatbox.
It can also be bought for 10,000 Reward Currency from the Tuska Comes minigame.
When Sacrifice is used, the player deals up to 100% weapon damage to their target regardless of protection prayers, and is healed by 25% of the damage dealt, or 100% if the ability kills the target.
Sacrifice is a basic ability. Unlike other basic constitution abilities, it does generate adrenaline.
While training combat, it may be helpful to time your hits so that you heal a good amount of life points from using this ability. Wait until your opponent is relatively close to dying, then use the ability. Do not use it too early or too late; otherwise only a negligible amount will be healed.
Sacrifice initially always did 100% of the weapon damage. This was changed on 17 December2013. The ability now deals damage up to 100%.
When released, the ability did not work with magic weapons. This was fixed on 17 December 2013. It can also be used without a weapon.
When released, it initially did not generate any adrenaline.
The ability only bypasses protection prayers from other players. It will not hit through the prayers of monsters such as Elite black knights.
During the third world event, Tuska Comes, this ability was available for 3,500 Reward Currency.
In PvP Sacrifice will always heal you for 25% of the damage dealt, and when the target dies it will heal you for 100% of the damage dealt on top of that. Essentially healing you 125% of the damage dealt in total. It is unknown if this is a bug or not.