I think it is not so fair with that only Light and Water get another rare card. So, the following cards are designed: They are either a powerful spell (but with a quite high cost) or creature with a useful ability.
Quantum Sink
Element: Darkness
Type: Spell
Cost: 15 Darkness
Effect: Empty all quantums from both player.
Concept: A powerful spell effect for mono-darkness deck. It also hosts rainbow, fire bolt deck and entropy shield, though darkness can always steal it….
Force of Nature
Element: Life
Type: Creature
Cost: 9 Life
Statistics: 1+X/1+X
Unity: X = number of Life creatures you control except itself. (Change at end of turn after battle)
Doppelganger
Element: Entropy
Cost: 9 Entropy
Statistics: 2/2
Ability: Shapechange - 3 Aether
Its power/HP becomes target's power/HP.
Untouchable
Element: Fire
Cost: 8 Fire
Type: Creature
Statistics: 5/3
Effect: Burning Aura - All spells and ability targets it become unless, that spell or ability 's controller loses 5 HP.
Flame from the Hell
Element: Death
Cost: 15 Death
Type: Spell
Effect: Destroy all creatures. For each creatures destroyed, you lose 10 HP. Empty all your Death Quantum.
P.S.: Don't know it is broken or not. I am just talking about Feral Bond + boneyard and waiting quantum for this. Though, Life + Death Deck seems cool. Also, a good partner with bone wall?... OK. If you have 10 creatures, this spell is stopped.
Time Walk
Element: Time
Cost: 20 Time
Type: Spell
Effect: You gain 1 extra turn after this turn. Empty your Time quantum.
P.S.: I think there is nearly impossible to produce 20 Time quantum in 1 turn?... A deck with 20 Time pillar and you play all of them?!...
Phoenix
Element: Air
Cost: 8 Air
Type: Creature
Statistics: 5/7
Ability: Immolation – 3 Fire, put it on top of your library
Effect: Add 7 Fire quantums plus 1 quantum for each other element to your quantum pool.
P.S.: I know phoenix seems to be more fire-like, though… it is still a flying creature which should related to air, except those dragons?...
Black Hole
Element: Gravity
Cost: 20 Gravity
Type: Spell
Effect: Destroy all creatures and sacrifice all your permanent.
P.S.: Will it have a use?...
Aether Storm
Element: Aether
Cost: 20 Aether
Effect: You cannot lose until your end of next turn. Empty all your Aether quantum.
P.S.: Will it be a bit difficult to program it?..