Pu Yanlan's White Nascent Soul was injured by this needle. After she went into seclusion, she was thinking of ways to remove the needle. It was only when she immersed all her consciousness into her Dantian that she discovered that bit of Demon Seed Essence was actually slowly repairing the White Nascent Soul's injuries. With every bit healed, a piece of the Demon Seed Essence would dissipate. By the time the White Nascent Soul was healed, half of the Demon Seed Essence had already dissipated, yet the White Nascent Soul had grown a circle larger,
"At that moment, an idea struck me, so I used this needle to wound the Black Nascent Soul as well..."
