The slow I proposed would limit riders that start in the spell zone to a single leap.
Some other ideas for elaborating on the spell concept:
As it is the (same) spell is cast by one or more piece types, but then affects every other piece type equally. But this could be made type selective with the aid of the captureMatrix: a special symbol (say $) in the position for the (active type, passive type) combination could make the passive type immune for the spell cast by the active type.
A useful new spell could be drop, meaning pieces in the hand could be dropped in the spell zone.
A very similar spell would be recall, which would allow pieces on the board to teleport to the spell zone no matter where they are.
The slow I proposed would limit riders that start in the spell zone to a single leap.
Some other ideas for elaborating on the spell concept: