Option should be there for spellbooks too

Great compromise to make the cheaper cards actually cheap again for those that want to rent low level cards. At the moment there are cards where levels 1 to 4 are all the same price to rent. This idea

How about keeping them common and rare but throwing in a small chance of a gold foil, say a tenth of the percentage for a normal pack? Would at least add a hope for something a little exciting.

I worry slightly about the monopoly castles and keeps have on trifoil runes, given that they are largely owned by large landholders what is their incentive to actually sell any? If they hold onto them