The thing is, they still fail to provide the truly deciding and useful example.

Such as my Flaming Sphere example above.

The tricky part is how to judge "most potent one". What does "potent" mean. We get no definition, so we have only natural language.

In my example above, I decided to go with the most generous intepretation, where the goblin needs to save versus the hardest DC and is subject to the most damage, even when they originate with different castings.

In this way, while castings of the same spell doesn't stack, they "cooperate".

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However.

I can definitely see a DM deciding to go with one or the other, but not with this amalgam of both. Perhaps for simplicity, or perhaps because the rules never say anything about amalgamating two castings.

So if your DM decides to simply say "the casting with the most damage is the one to use" that can't be contested - it's a very reasonable interpretation of the rule.

If your DM decides to instead say "the casting with the highest save DC is the one to use" that's also difficult to argue with.

Of course, your DM could go even further, and simply say something like "additional castings doesn't count". While indeed very simple and fast to use, it will have to remain a ruling rather than a strict interpretation of RAW, since it ignores the "use the potent" clause.

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