MOAR permanents. Isolation. Target creature does not attack for one turn, and takes no damage for two turns.
On the other hand, I feel that this series has too few spells for an "Element".
Here are some I quicky thought off:
Null Material
Spell
Cost : 4 Void
Target weapon's attack is lowered to 0 or target shield's defense is lowered by 1.
False Ascendance
Spell
Cost : 5 Void
Target creature gains Immaterial and a random buff (momentum, adrenaline, stat buff), but also gains an upkeep of 3 quantum per turn.
Voidmersion
Spell
Cost : 5 Void
Target card in hand has it's cost doubled and now costs Void.