Let's see:
Fear - Brings something new to the game but I don't like it in Darkness (Element has loads of good stuff already) and I think we should exploit the abilities we have, before tinkering with triggered abilities.
Add Pillar - Could use a "sexier" name, but it is definitely a card to consider that is easy to add and might add value.
Kitsune Trickster - The random creature part has been done sufficiently. I want to see more novelty.
Dark Matter - Sorry, but Black Hole is already in development and that card just collides with it.
Glitterdust - I really want options against immaterial dudes that exceed "just play more lifegain". I don't know, if Air is the best element for the card, but I want to see the concept done.
Desolation - I miss spells that attack the opponent's deck and I am inclined to vote for Desolation just because of that (and because of the well-calculated cost). However, I don't like the effect in Death. Maybe Time?
Wisp - Looks like a nice card to play and I want to see the "attack your owner" bit done sooner or later. However, the 0/8 doesn't match the name of the card.
Epidemic - These strong random effects look more at home in Entropy. Besides, the card is worded too vague to be considerable. Counts poison as status?
Silence - MonoLight is close to playable and this card might give it the final push. I'd hate to play against it but it could make a welcome addition to the metagame.
Main Gauche - Very nice weapon but the Element is off. Earth shouldn't be known for finesseful parrying maneuvers.
Spellbreaker - Nice, simple and efficient. I can imagine, voting for this one.
Lockdown - Interesting and maybe the last card needed to give MonoDarkness the final push to stardom. Only (but sizeable) No-Go is the name. You should never name a card just after its function on the field.
Inevitable: The "unshieldable" damage looks nice... until writing this made me realize that this is basically momentum
Loki: Repeatable stealing brings a lot of power. The card is good but I am afraid that it would decide too many matches on its own. So far, no single card has that much potential and it should not have.
Good News: Cute, but the effect is too small and too situational for me to consider building it into a deck.
Wolf: Too vague - Is "Friend" a random creature? Also, I am not sure whether Air is the right place.
Phoenix: I assume that you can only spend the quanta immediately and that it is mandatory. In that case, definitely conceivable.
Gamble: NO! We shall not reduce Elements to a game of Rock-Paper-Scissors. Next!
Dryad: I miss cards that give boni to other creatures, so this is a welcome addition. One of my favorites.
Abrasax: Fun idea and why not? There are other concepts that are more important to push, though.
Static Electricity: You should add something about the effect not being cumulative. Besides that: Very interesting concept.
School of Piranhas: But uhm... what IS a piranha?
Rampage: Lacks a casting cost.
Crusader: Its a shame that it is not going to work with Morningstar, isn't it? Couldn't you just have phrased it with "your weapon"?
Quantum Scales: Interesting fixer for Rainbow. But I just happen to want to push the other decks a bit more for now.