I need ideas for a steampunk and magic themed mod

Hello comrades,

Scattered around the world, the remains of two civilizations lie deep underground or high in the forest. The undergrounds were the realm of the Dwarves where they used the power of steam (lava and water) to power their machinery and allowed them to create powerful tools to conquer more and more the depth of the earth. As for the Elves, they use the mana of the flora to power their magic altars to create weapons and magic spells.

The both races lived in peace until the day the Dwarves started to lust after the liquid mana the Elves were producing because combined with plasma (an altered state of lava) it makes incredible amounts of energy. So war went on and the two civilizations were almost destroyed when a portal opened leading to a dark dimension empty from ressources where dark creatures lived. They managed to open this portal to steal the resources from Earth and ended both Elves and Dwarves. They now rule the Earth and are a deadly danger.

So this is the basic lore of the mod. Tell me what you need from such a mod

Addedum : 

I will be adding more details as the mod progresses.