Really great ideas here! I like the idea of warriors upgrading and gaining special abilities. And the theme of it being a duel just elevates the stakes! I also like how your current Level gives you access to those stronger warriors, but limits you board in other ways.
There were a couple pieces of information that I found a bit confusing on my first read through the board. Referring to "Level" as "X" might work to save space, but I felt it's less intuitive than using the full name. Also, I found the name "Training Ground" to be a bit misleading, since there's no real "training" or "improving" going on. Since it was the place where wounded warriors go, and they can't fight back if attacked, would it make sense to call it a "hospital"?