Story Time!
The Crystal Caves had often been a place of conflict. The gems within were a topic of conversation in every tavern for a thousand leagues, and there were many who were willing to risk death in order to get their hands on them.
Some called it a myth, but the wise know there once existed a single gem of six different colors the size of a mountain. For thousands of centuries the dwarf who controlled the One Gem controlled the Caves, but over time pieces were chipped off and lost, destroyed, or sent to far away lands.
As the wealth was scattered so was the power and many battles were fought trying to regain absolute control. Sometimes a great hero was able to take control for a time, but in a few generations at most, outsiders or battles over inheritance and succession would provoke conflict and blood would flow again through the caves.
Thousands of centuries passed some in peace and some in war. Castles were built at strategic locations, and as nearby gems were brought in for processing the castle's workshops adapted to more expertly handle the most common local gems. Secret tunnels were built between the castles and the gems they specialized in - to small to attack through, but perfect for quickly moving between friendly areas. And as troves of gems collected in the castles, a suprising phenomenon developed - they began to act as scrying stones allowing anyone to gaze into the gems and see into the other castles!
Now another mighty king has fallen and the Caves are once again in anarchy. Dwarven factions have arisen, each determined to take control of the crystal caves for themselves. Take your band of dwarves and conquer the Crystal Caves!
Just the Facts, Ma'am.
Crystals
Gem fragments (Crystals) are scattered throughout the caves. Control a cave territory with a crystal in it to earn +1.
Castles
The castles provide an excellent defensive bonus (+2). But maintaining a castle is not free, every castle you own will cost -6 for upkeep.
Fortunately castles are not just good for defense. Each castle contains a specialized crystal workshop (indicated by the flag outside), so gems of that color are worth 4x as much when you also hold the castle.
Control a castles to see how many units are garrisoned in the other castles.
Castles also have secret tunnels (not shown on the map) that allow you to quickly travel around your empire. The secret tunnels can't be used for attack, but if you already control a castle & one of it's gems, you can fortify between them.
Because of the limited space in a castle, only 30 units can be garrisoned inside.
Battle Axes
Territories marked with a battle axe have a +2 to attack.
Narrow Tunnels
Narrow passages in the caves allow only 6 units at a time in them.
Fortifies
Players get 10 fortifies each, and can return to attack from transfer.
Cards
Cards cycle between 16 and 32, and you can hold up to 8 cards, so think carefully about when to turn them in.
Strategy
First go for some convenient gems. Once you have 3-4 of a single color try and take the corresponding castle. Use the defensive bonus of the castle to secure one end of your empire and try to expend. Get a few more castles (and associated gems) and you'll be unstoppable!
Math
+2 to defense - expected loses of about 1.62 attackers per defender
+2 to defense & +2 to attack - expected loses of about .76 attacker per defender
no bonuses - exptected loses of about .85 attackers per defender