Soft Side

After learning about his secret Nephew Ben Amidala, Mortem's attitude changed. This is because for decades, or ever since he lost his carer, Jack never had knew he had REAL family, and thought when he lost Spe and his children due to childbirth, that that was it for him, and that Mortem would live alone forever. Learning that he has family gave Mortem something to fight for, making him conflicted.

When Ben and Darth Mortem finally meet, he sees that Ben is holding his old blue lightsaber, as Liam picked it up after their duel. This gave Mortem flashbacks to when he was a Jedi. Ben learns the truth, and now knows that Mortem is his Uncle. Ben's guardians gave him Spe's last name instead of Jack's "Skywalker" so that he couldn't be tracked by the Empire or The First Order, led by Supreme Leader Darth Mortem.