There are a few unreleased heroes that have been found within the game files. Some of them have all of their skills and SI items, while others only have a story.
Keep in mind that the unconfirmed heroes might not ever be released or could be completely redesigned in the future.
Japanese region exclusive hero. She will be coming to global servers soon though.
Nakoruru – Nature’s Guardian
Another crossover from SNK, just like Ukyo. You can take a look at her wiki here.
His background lore and skills have been found within the game files. Likely delayed for now.
Son of Shemira & Niru. The image above is official artwork released by Lilith for Christmas. Check the picture above the fireplace.
This hero is probably not going to be released anytime soon though.
Shown in the trailer for the Korean version of the game. He could be a Seirus skin, or perhaps his brother.