Getting cancelled should end a bunch of magical effects:
The spell of protection, rather than giving you a golden haze, gives you a “spectral shield”. It weighs nothing, and automatically equips into your shield slot if your offhand is free. It provides around 3 or 4 AC, and this does not degrade over time. However, the shield is temporary and will dissipate in a hundred or so turns.
If the shield is unequipped but kept in your inventory, it hovers around you and tries to block things on its own, but it only provides about 1 or 2 AC in this form. If it leaves your inventory for any reason, it dissipates. Casting protection again while you are already carrying a spectral shield resets its dissipation timer; it doesn’t give you a second one.
The shield has a price of 0, so you can’t sell it.
Flavor the spell of protection’s messages differently if you are a Priest.
The spell of protection does not gradually dissipate. It disappears all at once, with the player given a warning a few turns beforehand.
The effectiveness of the protection spell depends on how your off-hand is being used (open is better than carrying a shield, which is better than using it to wield a weapon). If your off-hand is free, the spell gives you a “spectral shield”.
