Talk:Mercenary Copilot/@comment-101.162.34.119-20170812095432/@comment-454133-20170812141819

You can modify a die any number of times, so Expertise and then Mercenary Copilot is fine. The limits are:

1) A die can only be rerolled once.  Rerolling is a type of dice modification, and it restricts future rerolling of that same die (but you can still do other modifications to it).

2) A die cannot be modified once an effect blocks further modification, e.g. Emperor Palpatine and Accuracy Corrector.

3) You can only modify dice at specific times.  Usually this is during combat, during the Modify Attack Dice and Modify Defense Dice steps.  The order players do this is very carefully set (cards like Juke care a lot -- see the Phases page for the steps).  You cannot spend a focus token to turn a bomb's focus results to hits, for example.  However, sometimes a card specifically says you can modify a die at different times, e.g. Emperor Palpatine can do it any time his team rolls dice, and C-3PO is any time his ship rolls defense dice.