The latest issue of Famitsu Magazine talks a little bit more about the newly revealed character Lyla as well as how battles will go in Tales of Zestiria.
As we reported before, Lyla is a Tenzoku/Divine of the Fire element. She is a Divine that dwells within the legendary "Holy Sword" meant for Doushis/Priests. For a long time now and due to an event in the past, she has been waiting for someone who can become the Priest. Upon meeting Slay, her hope is rekindled. Forming a contract with Slay, she now watches over him in order to make him into a full-fledged Priest.
The magazine also mentions that, ideally, a Priest should make a contract with 4 Divine of 4 different elements. However, no one has ever managed to do that so far.
So, 4 elements. With Mikulio for water, Edna for Earth and Lyla for Fire, all we're waiting for is the Divine for wind.
Now, on to battles: In Tales of Zestiria, the humans and the Tenzoku have their own fighting styles. Based on the info, it seems to be a bit similar to Tales of Graces F's battle system. From what we've seen so far, humans (technically, Slay and Alicia) are more in-tune with melee strike combat while the Tenzoku (Mikulio, Edna and Lyla) are more of mage-type characters.
This is further confirmed in the magazine: human characters use fast, close-range base artes with the use of the Circle button, while the X button lets them use more powerful arcane artes. For the Tenzoku, the Circle button lets them use mid-range base artes while the X button lets them use powerful, far-reaching Magic Artes. So far, there is no info regarding a regular attack button - just these artes, which makes it appear to be an adaptation of Tales of Graces' battle system of sorts.
The magazine also tells more about Mikulio and Edna's fighting styles. Mikulio uses a long staff, and is hence able to use mid-range artes at his disposal. Initially, he is able to accumulate spiritual energy and unleash them for stronger attacks later on. Some of his basic, strike artes are called ?? (Kiri Mizu, literally "slicing water") and ?? (Tachi Mizu, literally "reaching water"). As a Divine of the water element, Mikulio has water artes at his disposal, such as the classic Splash, and other magic artes called Twin Flow and Violet High. He's also able to heal, specifically more on individual party members. Edna, who uses an umbrella, has more close-range attacks. Some of her basic artes include Powder Snow and Sky, while her magic artes include Embrace End, Rock Lance and Air Pressure.
In addition, the magazine mentions that the dragons are so-called "Apostles of Destruction."
Also visit Famitsu for actual screenshots from their article. And thanks to @Kurushii for the magazine pages.