This spell will be able to target cards in players hands? Thats odd, but potentially quite powerful.
It could be devestating to mono / duo decks if used offensively.
If used on your own cards, it would essentially allow
to use spells from any other type in an other wise mono
deck.
If used on nightfall, would it change the color of the cards affected?
e.g. target nightfall with a light mark and make it affect light creatures instead of dark and death. It kind of reminds me of the magic card "Sleight of Mind"
Would be tricky to code though, I'd imagine