Hey, thanks for playing, yeah we are surely missing a tutorial here and there ...
and it all is far from finished ... it will be ... eventually
however, the main mechanics should be working ... more or less
since you were able to go to the arena I assume you were able to create a boss ...
then when you threw your boss in the arena it was empty is that what happened?
btw if you don't mind, what browser are you playing it with?