Marrow Thief node for Bone Curse - “If you kill an enemy affected by Bone Curse you have a chance to gain Bone Armor”
Node grants 10% chance on kill to gain bone armor up to 30% at 3 points however I have never gained the bone armor buff from Bone Curse when using this node whilst levelling a Lich to level 50. I have tried it with the kill threshold node [with no others active so the Bone Curse one is the highest value], assuming bone curse would be triggering the kill on the enemy mobs [in case it was a mistake in the wording of the tooltip], but that hasn’t granted the buff at any point either.