I'm not sure if its a bug, oversight or simply bad design choice but if player puts 2 or more vampires together in arena then they will fight forever.
This basically dismisses entire effort needed to maintain them and gives player unbalanced way to gain "titan level" overpowered units.
They are always at 100% blood, they dont need to eat prisoners because player can just keep them forever in arena until he uses rally flag.
They quickly level to 10.
They dont take gold while fighting in arena so player can basically never pay them because they are either fighting at rally flag or in the arena.
They never get unhappy or rebel when fighting in the arena no matter how long they are there.
Proper fix would be to not allow them to fight in the arena (make them not droppable there) and only allow them to train in barracks so they still need to eat prisoners and pickup gold from treasury or rebalance vampires altogether.
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