So, this came up in a game and I decided to rule it one way since I couldn't find (admitting it's possible I missed it) that it would play out like so: I announced I was going to deply Burna Boys, I exhausted the Bigtoof Banna the reduces the cost by one, in response my friend/opponent played a card that destroys a limited card on the field (forget the name) after I exhausted it. We agreed to rule it that it negated the support reduction and thus I was unable to play Burna Boys (because I only had three resources). So my question would be, was that the correct one this would have played out?

The card that was played that destroyed the support - was the effect an Interrupt? If not, then no, this was incorrect.

Unlike Magic you do not play cards 'in response'. An effect is triggered, and resolves. The only way to prevent that resolution is with an Interrupt that somehow negates the original effect, either by directly cancelling or otherwise making the play invalid.

Commissar is correct.

I'm assuming the card your opponent used was "Calculated Strike" (Action: Destroy a target Limited card).

Because that card is an "action," it cannot be used while another effect is being executed. Once it was your turn and you started Deploying your Burna Boyz, your opponent could not play an "action" effect until your deployment was completely resolved. Essentially, he cannot wait until after you trigger your Bigtoof Banna and "undo" its effect by destroying it with this card. He has to anticipate your need for it and destroy it before you get a chance to trigger it.

Now, if "Calculated Strike" started with "Interrupt" instead of "Action," you would have been correct. As Commissar describes, Interrupt effects are used between the initiation and resolution of an effect, so could stop the cost reduction from happening. So your instinct on this interaction were not entirely wrong -- you just failed to take into account the kind of effect being used and whether it was the correct time to use it (it wasn't).

That makes more sense, rookie mistake I suppose but thanks for clarifying and being so helpful! And yes it was Calculated Strike, I went back and looked after posting

Hey guys, one last question cause I was scanning through the rule book again and got slightly confused about the units that come with a Commander, I get how they come in but my question is this: When you win the battle at planets 2-5 would the units that come with Commander leave with him or stay on the planet? The way I understood the rules was they would stay on the planet, but figured I'd just clarify to be sure.

Army and token units would only leave planet 1 after the battle. At 2-5 they would stay there. Warlords always leave.

Thanks!