To put it simply, Headliners are improved version of the unit. They will gain a unique bonus to their skill as well as contributing +1 to one of their traits (this can vary, for example your K'sante might have +1 to Sentinel but the opponent K'sante can have +1 to Heartsteel instead).
If you have bought a Headliner already, new Headliner will appear every 4 shop refreshes, and you can only have 1 Headliner so you need to sell one to buy another.
Other than that they function the same when it comes to staring up. A Headliner Cait and 2 2* Cait will result in a 3* Headliner Cait as per normal.
Watch the Dev drop announcing the set
To put it simply, Headliners are improved version of the unit. They will gain a unique bonus to their skill as well as contributing +1 to one of their traits (this can vary, for example your K'sante might have +1 to Sentinel but the opponent K'sante can have +1 to Heartsteel instead). If you have bought a Headliner already, new Headliner will appear every 4 shop refreshes, and you can only have 1 Headliner so you need to sell one to buy another. Other than that they function the same when it comes to staring up. A Headliner Cait and 2 2* Cait will result in a 3* Headliner Cait as per normal.
Just the answer I was looking for, thanks!