This is Savina's first art from 2017, before any of the Heaven Hunters universe was planned. I used to stream art on Twitch every day, so she was a character that I designed on stream because I didn't have a plan for that session.
Here's her current design. I simplified her design a ton, and boiled her down to her essential elements as much as I could, not just to make her more iconic, but also to simplify the process of drawing her for each panel. Most notably I dropped the tail and spell tattoos (mostly because I kept forgetting to draw them haha oops), and her face changed a lot during that process too. Also, her horns are no longer striped.
Here's Nira's first concept art, drawn a couple weeks later. The file is still named "Demon Friend1.jpg" 
And here is her design from issue 3. Her ears and horn have changed over time, and I straightened her hair because it's a lot easier and quicker to draw.