More info about Tales of Link is out from the latest issue of Viva Tales of Magazine which clears up some of the things we've been wondering about ever since the game's announcement.
First off, eczema the "Messiah" is actually you, the player. Tales characters are also in the game along with other Tales of Link original characters. As you'll see from the scan above, the Tales characters have been given completely new artwork for the game.
In battle, as seen in the above scan, there are a total of 9 characters in active battle at one time. There are 3 other characters at the back of the front lines that will be in rotation - hence the actual number of characters in the party is 12. Whatever the level of the player is, that will be the level of the characters.
This part isn't that clear, but making a "Friend" allows you to insert their characters in your party. As seen above, the images from left to right indicate your Leader character, your Sub Leader, and your Friend's own Leader and Sub Leader.
There are symbols at the feet of the characters called Brave Linker which I believe change from time to time or something. When you touch characters together with the same symbol (i.e. you drag on the screen), a Link is formed from this team, and when you let go, these linked characters will then attack. And if you manage to actually put 9 characters on screen to be involved in a Brave Linker, a Hi-Ougi/Mystic Arte will be performed. There's also an indicator above that says which Brave Linker marks will be coming up during the next rotation.
So far, confirmed Tales characters that will be in the game include Asbel Lhant (Tales of Graces), Senel Coolidge (Tales of Legendia), Leon Magnus (Tales of Destiny), Suzu Fujibayashi (Tales of Phantasia), Judith (Tales of Vesperia) and Colette Brunel (Tales of Symphonia, plus Sophie (Tales of Graces) for the iOS users who pre-registered for the game. A lot more characters were confirmed but it's unsure yet if they'll be in Link's main story.
Thanks to lunawings from Tumblr for the scans.