Thunder_Gr
Emperor
One turn is all you need to create an expendable army instantly from nothing, take a city with them, and be able to do it all over again.
It can be done, if the cities are close to eachother and have not many defenders. But in order to do it, you must have a few death mana sources + combat 5 + Spell Extension II to your Eater for this to work, and the enemy must be really careless with the defences. If you sum it up, you can never really have more units+summons than the opposition can field. Even with 10 warriors the enemy can prevent you from taking the city, since it does not matter how strong the defenders are, just so that the summons cannot break through. In addition, the Eater of Dreams needs at least 3 turns to reach the new city, since he won't have mobility, most likely(if he was up to the task of tackling the city with summons), in order to repeat the process.
I don't say it cannot be done, on the contrary, this is what the unit is designed for. It is very powerful, but if it wasn't, the Sheaim would have no purpose in this game, apart from being someone for the other civs to feast on.