Dagger to the Heart
"She needs a new heart, or there's no saving her."
Xerxes spoke up almost instantly, "I can give her mine."
The demon lord looked down upon us, laughing sinisterly, "We can't. Only the immortals can switch their hearts with a Wisteria."
His right-hand man raised a brow and said without hesitation, "That's easy—just kill an immortal."
The demon lord shook his head, and breathed words that left me despairing, "It must be given willingly."
Xerxes was silent this time. Was there any immortal who would willingly give up their heart?