It is a new RPG developed by the new Studio Istolia and produced by Hideo Baba, former producer and manager of the entire series Tales of.
Baba, who previously worked at Namco Bandai, is producing the project.
The studio is apparently looking for Battle planners and programmers with action RPG experience, which gives us some indication as to what we can expect from Project Prelude Rune.
Square Enix has both a new role-playing game and a new studio making it. However, the studio's stated mission is the focus on storytelling in games and to bring those experiences around the world.
With the vague promise of further details "at a later time" and no mention of a release schedule or platforms, all we have to go on is the concept art and two sketches (all shown in the slideshow below, via Gematsu). Square Enix did not reveal much else about the game, but did say it aims to build an RPG "with a new fantasy: unfolding across a vast land teeming with life".
In Tales land, meanwhile, Tales of Berseria has just landed on PC and PS4. "Istolia" apparently originates from the Greek word for "story" and is, in Square Enix's words, "central to the studio's primary value".
For now, that's all Square Enix and Studio Istolia were willing to share about Project Prelude Rune.
Hideo Baba is working as the producer of "Project Prelude Rune" as well.