I don't mean to come across as OVERLY negative (just a little negative), but what's the difference in all these toy approaches and applications of LLMs? You've seen one LLM play a game against another LLM, you've seen them all.

I was thinking you could formally benchmark decks against each other enmasse. MTG is not my wheelhouse, but with YGO at least deck power is determined by frequency of use and placement at official tournaments. Imagine taking any permutation of cards, including undiscovered/untested ones, and simulating a vast amount of games in parallel.

Of course when you quantize deck quality to such a degree I'd argue it's not fun anymore. YGO is already not fun anymore because of this rampant quantization and it didn't even take LLMs to arrive here.

XMage is a decent client and being able to see and watch the games is useful.