Right. I know there is a lot of controversy over this topic atm, about whether or not is an exploit to create an army of priests following you around...etc.

While on the one side, having more than the 2 priests you are intended to have makes a demigod much harder to kill, the demigod can't summon back the priests they've lost without returning to the citadel. They also waste a lot of time and money in order to carry out this "cheat".

How about this: All minions summoned by idols are weakened. Now, when you have the correct idol for a particular type of minion in your inventory, those minions receive a buff (powering them up to how powerful they should be). Extra minions who are "exploited" into the game are a lot weaker (mainly the priests having a longer cooldown, less powerful heals, less health/mana etc you get the picture).

Hopefully this would encourage players to not waste money on summoning extra minions, and we would see less and less of undefeatable Sednas running about the place.