It occurs to me that even in the Trainer, this would be quite hard to accomplish.
For those who don't know how this works, if you Parallel Universe a creature while it's in the middle of a Dive, the creature created will have the doubled ATK. You can double that ATK again by Diving the new creature, but after one Dive it goes back to the ATK it's "supposed" to have.
So round 1 you have a Wyrm with an ATK of 5. You Dive it, making it have an ATK of 10, then Parallel Universe that, giving you 2 Wyrms each with an ATK of 10. You end your turn and the original Wyrm goes back down to 5, but the copy stays at 10. On round 2 you Dive both Wyrms, so you have 1 Wyrm with an ATK of 10, and 1 with an ATK of 20. You end your turn and both Wyrms go back down to 5.
This means that you can chain Parallel Universes. Parallel one Dived Wyrm to get one with an ATK of 10, Dive that and Parallel it to get one with an ATK of 20, Dive that and use your third Parallel Universe to get one with an ATK of 40, Dive that an Parallel it to get one with an ATK of 80, Dive that and use your 5th Parallel Universe to get one with an ATK of 160, Dive that and use your last Parallel Universe to get one with an ATK of 320, and Dive that to get one with an ATK of 640.
Theoretically, that's possible. The problem is that you're almost certainly going to kill your opponent before you get that far, especially with an HP cap of 500 and the AI not using Stone Skin unless not doing so would kill it. I think perhaps that the only way to successfully do this would be to use something like Shockwave on the Wyrm you've just copied in order to prevent it from attacking. I suppose you could also use Holy Lights and Purifies to help heal your opponent.
So that's my challenge - can anybody use the Trainer to get a Wyrm with an attack of 640? Bonus points if you use Blessing/Unstoppable/Chaos Power to the first Wyrm to get something exponentially huger than 640. Oh, and NO Shard Of Patience. That would be too easy. Sundials can be used, but you get extra credit if you don't use them.
If anybody can do this, then post a screenshot, as well as a description of what hand you had, what hand the AI had, and how the match went.