Tier 2 Blood Rapture rune: found in Cursed and Defiled Chalices by a random chance.Tier 1 Blood Rapture rune: dropped by the Shadow of Yharnam boss.Tier 3 Blood Rapture rune: +300 HP per visceral attack.
This is useful in most situations where your health is in a pinch and can be the difference between life and death. The effect it carries is giving you HP after visceral attacks. The top rune spot belongs to the Blood Rapture rune.
