ON THIS WIKI
Life Essence is the magical energy used in Blood Magic. It is similar in purpose to mana, but producing and consuming it is different.
Life Essence has two forms: the liquid generated in altars that can be pumped and placed in the world, and the essence stored in a network. The mod author calls both Life Essence. Since this is a little confusing, players tend to call essence in a network LP and essence in fluid form blood.
It is possible to turn LP in to blood with a usage of a Cry of the Eternal Soul Ritual built around the altar.
A sacrifice is required to generate life essence. These sacrifices are usually performed at a Blood Altar. There are two types of sacrifice: the sacrifice of oneself, or the sacrifice of others.
A beginning mage must sacrifice their own health. This is done by right clicking a Sacrificial Knife at an altar. Each use of the knife will generate a small amount of essence at the cost of a heart of health. The essence will be stored in the altar in its liquid form. This liquid essence can be used to transmute items or be transferred into a network for consumption by items, spells and rituals.
More experienced mages gain the ability to sacrifice mobs to fuel their altars. This is done by left-clicking a Dagger of Sacrifice on a mob that is within a few blocks of an altar. This will instantly kill the mob regardless of its remaining health and generate liquid essence in the altar. Both passive and hostile mobs can be sacrificed. The amount of essence gained depends NOT on the health of the mob has when it is sacrificed but the type of mob sacrificed. There are 3 types of mob that will give different amounts of blood: Passive (Animals) will give 250LP, Unredeemed (Zombies, aggressive mobs etc) will give 500LP and Innocent (Villagers and Players) give 2000LP. Sacrificing Villagers was going to have consequences using a karma system but the idea was scrapped as it was not deemed to fit with the theme of Blood Magic.
Advanced mages can automate these processes with the Ritual of the Feathered Knife and the Well of Suffering. Runes of Sacrifice and Runes of Self-sacrifice can increase the amount of essence generated per health sacrificed.
Transferring essence from an altar into a soul network requires the use of a Blood Orb. The orb acts as a conduit for transferring the essence into the network, but is not a container for it. Losing an orb will not cause the loss of any essence in the network. The maximum amount of essence that can be transferred in to a network is determined by the quality of the orb used to do the transfer. Runes of the Orb can increase this limit.
To transfer essence, place the orb into the altar by right clicking on it. The altar will begin to lose essence and the network the orb is bound to will gain it. This process emits red particles. The Divination Sigil allows a mage to monitor the amount of essence in his altars and network.
It is also possible to transfer essence into a network directly by right-clicking an orb. This will sacrifice a heart and add 200 LP to the bound network. This does not require an altar and can be done from anywhere, but is less efficient than an altar with Runes of Sacrifice or Self-sacrifice.
Any item that uses essence will draw that essence from the network of the player it is bound to. This process works over any range and from any dimension. It is important to note that the essence always comes from the bound network, even if the item is used by a different player.
If there is not enough essence in the network to fuel an activated item, such as a Water Sigil, it will draw life essence from the player using it by sacrificing their health. If the amount of essence needed is high enough, this process can kill the user. Note that only the player using the item can be killed in this way, so even if a mage's bound items are stolen, they cannot be used to remotely kill him, only to drain LP.
Passive items, such as Rituals or Lava Crystals, will instead cause the bound mage to suffer nausea, causing the screen to warp and wobble around in a disorienting manner. This effect lasts until life essence is added to the network or the ritual is deactivated. It is considered a rite of passage among blood mages to run out of essence in their network and be suddenly struck with nausea while far from home. The effect is quite disorienting and can make the trip back long and difficult.