Huh. First Tachie and Mash fanart I've seen - hell, first Tachie fanart I've seen. (Tachie was an early Shielder concept created for Studio DEEN's Fate adaptations, but for various reasons she never got used. Mash ended up being the first Shielder to see the light of day.)
See this is how you make use of early concept art and boom you created another character without trying. She looks like an inverted Mash, black hair and crimson eyes, opposed to Mash's lilac hair and lavender eyes.