Lore appeared to be a sort of life essence; a measure of a creature's vitality and how difficult they were to kill. As Kain drank the blood of his enemies, he could also absorb their Lore and add it to his own. The blood would sustain him, but the Lore would eventually make him stronger and harder to kill. Practically, this meant his blood vial would lengthen, and his body would retain more healing blood. He would be able to withstand more injuries before he was destroyed.
Kain could only gain small amounts of Lore from the weaker, non-confrontational humans, but much more from stronger adversaries. Umah instructed him to "leave no enemy alive". Kain could also acquire Lore from Lore Coffers. These chests were described by Umah as relics of their vampiric ancestors (presumbly meaning the Ancients), and they were scattered throughout the game. Only vampires could open them. Coffers marked with blue circles held more Lore than those with red circles on them.[1,2]
- [BO2] Umah to Kain: "Blood is your life. Without it, you will die.
If you are wounded, seek out blood to restore your vitality. You must know too that by drinking the blood of others, you will gradually become stronger and harder to kill. We call this a vampire's Lore.
The more creatures you drink from, the more Lore you will gain, and the greater your health will become. Leave no enemy alive, Kain. You will need their blood and their Lore to survive.
Now, let us continue."
- [BO2] Umah to Kain: "Also know that scattered throughout Meridian are relics of our ancestors. Useless to humans, only vampires can access these coffers and use the power within. Seek these out on your journey."