THE SUMMON ALTAR (available at TH8)
Many people say that additional heroes are ruled out, well dont be decieved and read the rules yourself. I assure you they are not ruled out, but they might be unbalanced. Having more than 2 heroes will indeed cause a gap between the players with and without them. But i think I have the solution.
Introducing the summon alter. This alter would resemble the barbarian and archer alters, but with no special crown on it. Instead, It has a bird bath-like dish in the center. The alter would be like the barracks and unlock more heroes with each upgrade. The altar can house one hero at a time. Several examples of heroes could be a giant, a wizard, a dragon, and a goblin. In order to summon a hero, you must make a worthy sacrifice.

Each hero is bought with a different resource. For example, the Giant could cost trophies to summon, the wizard could cost spells, the goblin could cost elixer, and the dragon could cost gold or gems.(just examples) Each hero takes different ammounts of time to come once you summon them and sleeps on your altar till you use him. These heroes would not be able to defend but could be when attacking. And the ammount of heros per attack would be two, and high power heroes like the dragon and wizard would take up the space of two heroes. And if multiple dragons and the dragon hero seems OP, the dragon hero could be "territorial" and scare away other dragons( including your's) that are too close(probably 15 tiles) meaning that no dragons could come near it, even to help it. If u like it, let me know and ill develop it more and add heroes.