This is a regression from the original DOS release of the game. In the DOS version, running a level via the -level command line argument uses the spell inventory set in the level file. However, in the port it seems to be using the campaign acrued inventory, and because there are no spells yet acquired this means the inventory is blank and so it's impossible to play levels loaded this way properly.
It's notable that the new--custom_level argument does not have this problem, and uses the level file inventory.
This is a regression from the original DOS release of the game. In the DOS version, running a level via the -level command line argument uses the spell inventory set in the level file. However, in the port it seems to be using the campaign acrued inventory, and because there are no spells yet acquired this means the inventory is blank and so it's impossible to play levels loaded this way properly.
It's notable that the new--custom_level argument does not have this problem, and uses the level file inventory.