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He then claimed that each Valakut triggered 5 times (killing me). I am doubting this now.
Here is my reason: The two Valakut cards entered at the same time as the other 5 basic lands. That means when they were on the battlefield and their ability was in effect, the other 5 basic lands were already there too. That seems too late to trigger a "Enters the Battlefield" effect.
So here is my question. Am I right or wrong? If I am wrong, please show me how the enter the battlefield effect can trigger for something that enters the battlefield at the same time as itself.
If I am right, please show me the rules that prove it. I now have two shop owners that are convinced that this is a legal play. If it is not legal, I am going to need clear rules citations to convince them.
Side note: If I am wrong and it is a legal play, then I have a follow up scenario. Say I have 2 Champion of the Parish cards and 5 other human cards in my graveyard. If I play a spell that lets me return all of them to the battlefield at the same time (say Angel of Glory's Rise), would the Champion cards get 6 +1/+1 counters on them?