
1. Elf Princess Nuala (Hellboy II: The Golden Army) shared a psychic link since birth with her brother, Prince Nuada. Any wounds inflicted on one were transmitted to the other. Nuada despised their father, King Balor, for making peace with humanity. Nuada killed Balor and awakened the Golden Army with the intent to exterminate humanity. During the final battle, to save Hellboy and stop her brother, Nuala stabs herself in the chest, killing both Nuada and herself.

2. Draco (Dragonheart) saved the life of wounded prince Einon by sharing the half of his heart. This also made Einon immortal as long as Draco lived. Unfortunately, Einon grew up to be a despotic king whose cruelty led to a popular uprising. To defeat Einon, Draco sacrificed his life, allowing the knight Bowen to plunge an axe into his heart.

3. Pandora (GoW 3) was created by Hephaestus as the key to Pandora's Box. But Hephaestus came to love her as his own daughter and hid her from Zeus, suggesting that Kronos be used instead as the perfect guardian of the box. However, after Kratos used Pandora's Box to defeat Ares, Zeus became terrified of the box's power and tortured Hephaestus until he revealed Pandora's location. Zeus then hid the Box in the Flame of Olympus, so that only Pandora could open it, and kidnapped Pandora, placing her in the Labyrinth created by Daedalus. However, Kratos managed to find Pandora and bring her to the Flame of Olympus. Kratos hesitated before using Pandora, who reminded him of his deceased daughter, but she decided to sacrifice her life to help Kratos. She extinguished the flames, and Kratos was able to open Pandora's Box.


[Sad trope] Kind characters, whose deaths are necessary defeat the villain (spoilers about Hellboy II, Dragonheart, GoW 3)