You cannot choose more than 2 heroes during setup.

Setup: Choose a non-neutral unique ally from your deck and put it into play. Add the sum of that ally's printed , , , and hit points to your starting threat. Then, flip this card over and attach it to that ally.

“I am a messenger of the King,” he said. “You are speaking to the King's friend, and one of the most renowned in all the lands of the West.”
–Pippin, The Return of the King

Attached ally loses the ally card type and gains the hero card type.

Attached character cannot be readied more than once per phase.

Messenger of the King is immune to card effects while attached character is in play. If attached character leaves play, remove Messenger of the King from the game.