I reckon invisibility with this card would be a good idea, since not too many decks are based on spells that target Opponents hp, although i know some PvP decks that do intend to use fire bolt as either a finisher or fire quanta stacking for a KO firebolt barrage.
Also Ive seen some decks that use Lightnings to target Opponents hp as a finisher, gather 4 of them in hand, after creatures lower opponents hp, you could finish off opponent with 20 damage.
Also another spell that is mostly used in rush Air/fire decks is unstable gas, that one is pretty dangerous, instant 20 damage.
I actually support this card since it doesn't necessarily have the same mechanic as jade shield, but rather absorbs spell damage.
Since that is the case, I suggest making a poll for whether this should be invis or not.
In the case of it not being Invis, it would still screw up decks that rely on heavy damage spell barrages such as unstable gas or fire bolt.
Invis would be more of a huge compliment, taking opponent by surprise.
though I like the idea of introducing invis permanents, IF cloaking can be deactivated (say Pandemonium), so then its not OP.