You can only use this effect of "Black & Blue Skull Dragon" once per turn
Things are, generally speaking, getting better
(2023-06-16) The trigger event doesn't have to specifically refer to legendary permanents or to artifacts, nor does it have to specifically refer to when something "leaves the battlefield." For example, an ability that triggers "whenever a creature dies" would trigger twice if a legendary creature or an artifact creature dies while Gandalf the White is on the battlefield, as would an ability that triggers "whenever a permanent is put into a graveyard from the battlefield." (2023-06-16) Look at each legendary permanent and each artifact as it exists on the battlefield, taking into account continuous effects, to determine whether any triggered abilities will trigger multiple times
2 Miirym, Sentinel Wyrm Here There Be Dragons One of the premiere Dragon commanders, Miirym, Sentinel Wyrm not only doubles all your Dragons, but sticks around thanks to that ward effect
Possible Card Choices for the Chaos Emeralds While its the least likely to be the case, there is a slight possibility that a Chaos Emerald card would be a skin for Mox Emerald