This game makes use of the classic Build Engine that runs many 90s classic games.
If you didn't notice lately 90s inspired FPS games are not uncommon but only recently these started to actually capture the spirit of the genre, and Ion Maiden is among the later ones.
After loosing Duke Nukem rights 3D Realms released Bombshell, a top-down shooter that was supposed to be a new entry in the Duke series but it was mediocre at best. This doesn't means they abandoned their new protagonist and in fact (Bomb)Shell is back in Ion Maiden, a prequel to Bombshell, made with eDuke32 a modern and enanched port of the BUILD engine that powers many classics like Duke Nukem 3D, Shadow Warrior and Blood.
The game looks intersting and being made with such antique game engine should help obtain the classic feel of the genre. Ion Maiden is out today in Early Access on STEAM, DRM free directly from 3D Realms and it will be available on GoG, if you want to see it in action check the trailer below.