More dragon suggestions:
When a flying dragon dies, it's death animation MUST be as close as possible to the scene in Dragonslayer where...
Spoilers...
The old wizard exploded and the dragon fell into the lake.
End Spoilers.
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Also I propose different dragon races that can be recruited:
Fire: Red, breathe fire, direct damage + damage over time burn effect. Similar to the young dragons now but red.
Earth: Green, breathes toxic fumes, direct damage + nerf to strength, constitution and other attributes.
Air: Blue, breathes lightning, high chance to miss but high chance to crit with very high direct damage, also maybe a stun effect, and higher chance to hit against metal armor.
Water: white, breathes frost, direct damage + slowing effects on movement and combat speed.
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One thing I really like is how the diplomacy tech tree can be used to recruit intelligent spiders, bugs, and dragons. I already like diplomacy when it can be used to get the AIs to fight each other, but recruiting monsters adds that cool-factor to the tree.