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In general, if we're talking about it, it would make sense to slightly increase the cost of buildings for Tier 7 units, but also strengthen them and increase their recruitment cost. As for Necromancers, it would be logical to change the formula for raising undead for dragons (if possible) or slightly weaken the overall formula, but at the same time, give them decent Tier 7 units. I have an idea about this; we could recolor the bone dragons to green (or not recolor them), give them the ability to shoot clouds of poison (similar to Draconians), and create a corresponding animation (they already have an animation where they yawn; we could give them a Lich-like firing animation and attach it). We could do the same with other dragons, but change the color of the poison clouds to match. We could even leave the same stats, but reduce the range to half.