Ya I realize you just unlocked 14* titans but you should really plan to add something special at lvl 15 like an ursena type fight w minion spawns (One that taunts and one that silences).
A better idea to give it logevity is make it 2 stages like ursena. If you kill the first stage you get normal 15* Titan rewards. Then make the Second stage rare without minions so that it has an increased chance at 4* items and maybe additional rewards. If needed you can have it reset to 14* titans win or lose… meaning you need to kill 4x 14* titans again to get the 15* Titan.
With a lot of people unlocking the hunting lodge it gives a better reason for this. Make it part of the new expansion.
I don’t expect people to kill the second stage for a while but it’s there to strive for and done this way means you can make it hard without forcing people to always fail at 15* titans since it becomes a choice to go for it or not.