When minig a Crystal, do I keep each collected Crystal in a stack of its level or should I make one big pile?
Officially recommended: partially hidden. The points are hidden, but the total amount of Crystals should be visible.
Are the skills of the cards optional or mandatory?
The use of card skills is optional.
When buying Artifacts, do you get the benefit immediately or at your next "Artifact activation phase"?
If the Artifact needs to be activated to use it - next phase, if it doesn't - immediately.
"Mass production" card: "Worth 2 VP for each set of three Crystals you own." What kind of set? A set of three Crystals of the same color? Or the same level or both?
You get 2 points for every 3 Crystal tiles collected.
If I pay/play more Mercenary cards for mining/hiring/artifacts/etc. at once, can I choose the order in which they will be stacked?
You can choose the order in which the cards played will be stacked. To be precise, you can choose the order only if you use multiple cards in one Action, not many different Actions.
Are Cave-in symbols treated as "unique symbols" for the purpose of scoring?
Only the faction symbols are counted during scoring.
Can I carry out Actions resulting from Mercenary cards and raid a Base in the same turn?
If a player has not taken any of the 2 possible Actions, the Action of the Leader can still be taken, either before or after raiding the Base.
If I did not have the Leader before, does the first Mercenary played become the Leader?
A Mercenary played does not automatically become the Leader. The Leader is only designated during the Starting Phase.
Does the order of the Artifacts placed under the Command card determine the order in which they can be activated?
The order of Artifacts placed under the Command card does not determine the order of their activation.
Do all the cards played must be of the same color when mining Wild Crystals?
The rule for mining Crystals is always the same. The difference with Wild Crystals is that you can use cards in a different color than the Wild Crystal color.
Can I mine a Crystal when not all the cards played are in the same color, but the sum of the card levels in the appropriate color is equal to/higher than the cost of mining the Crystal?
All the cards played must be of the same color.
Do I lose the played cards?
Place them face up in your play area; do not put them in your Base just yet. At a later stage, you will transfer them to your Base in the order in which they were played. If you decide to raid your Base in the future, you will take the cards back to your hand.
Can I change the order of cards after they are played?
The order results directly from playing them. You cannot change the order of previously played cards.
Can I take the same action twice in a single turn?
In their Action Phase, the player cannot perform the same action twice unless another rule allows it. For example, Hy'dran Fish'Bean as the Leader allows you to take two identical actions.
Does the player playing their turn play all three phases at once, or does it alternate with other players?
The active player plays all the phases on their turn, only then the next player plays.