It is kinda hard to figure it out just based on that teaser- but i really hope Aurelion Sol is PURE creature champion. What i mean by that is, i am hoping he isnt humanoid beast - like Shyvana or aatrox, we kinda need bit more regular beasts - like Rek sai or Cho Gath.
Also, when it comes to abilities, it would be nice if they are elemental related (at least name implies that this is possible), beside this, him being a hard control mid champ. would be good. It would be a nice introduction into mid season mage updates.