Eriisi Bio
A demon born in the first plane of the Netherrealm. She was part of family of Netherrealm inhabitants who were still loyal to Lucifer many years after his defeat at Shinnok's hands.
The Brotherhood of Shadow discovered the family dared to follow a leader different from Lord Shinnok and ambushed them, trapping their souls in the Prison of Souls. Eriisi was the exception, since she was a young child at the time and the members still believed she could be reeducated to serve the true ruler of the Netherrealm. She was forcefully recruited in the Brotherhood of Shadow since then.
Unexpectedly for the members who took her in, time didn't make her forget her past or what they did to her family. She tried to escape many times, failing in the process. The leaders of the Brotherhood group she was in, despite considering also taking her soul to the Prison of Souls for rebellion (as was recommended), were 'compassionate' enough to 'just' reprogram her mind through magic to behave accordingly. Luckily, someone interrupted that process.
Geras was a being created by the Elder Goddess of Time, Kronika, one of her three children alongside Shinnok and Cetrion. Although he was recommended by his mother to stay neutral in the conflict of mortals, his curiosity made him visit other realms from time to time. He visited the realm ruled by his brother at the right moment.
Geras was horrified when he heard that Eriisi's free will, something the Elder Gods valued as the greatest right of mortals, was going to be taken from her. He decided to save her and, since she had nowhere else to go, he took her in. As time went on, their relationship became that of a father and his daughter, something they are willing to openly admit nowadays. They have learned much from each other in their time together.
On the one hand, Geras has taught Eriisi the wonders of peace, since he thought that would have been something neither the Brotherhood nor the Followers of Lucifer would have put enough emphasis in. He even let her visit certain parts of other realms as examples, and she was fascinated to have the chance. It gave her motivation to one day fight to change the current state of the Netherrealm so it can be like that. Once she encounters other rebellious demons like Sareena and Ashrah, she may have a better chance to achieve it than she expected.
On the other hand, Eriisi's rebellious spirit and motivation to change things has inspired Geras to abandon his neutrality. It maintaining it meant that countless people through the realms had to went to tragedies like hers while he did nothing, then he just couldn't maintain it anymore. He was going to fight for what he believed was right, and Eriisi's dreams to change her realm was part of it.
Shinnok's family is definitely going to give him more trouble in the future than he had expected.