Feelin' Blue...

[Istanbul]

What you have to realize about Fading Signals is that it basically reads "Remove target player's library from the game". Sure, a few cards might be lucky enough to escape, but you've basically spent 3UU to kill your opponent. The drawback on something like that SHOULD be absolutely enormous. Remember Apocalypse? That's the kind of thing I'm thinking about, except Apocalypse wishes it was this good.

This would be fair:

Fading Signals (3UU)
Sorcery
Look at target player's library. You may remove any cards in that player's library that share a name with another card in that player's library.
For each card you remove from that player's library in this way, that player may look at your library and choose a card. Remove cards chosen in this way from the game.

Mercury Elemental is broken. It's just that simple. Sure, you can Disenchant or Stone Rain it...but (A) that means you aren't using those utility cards on their intended targets, and (B) you have to be playing the appropriate cards to even use its effect. Add 1 to the casting cost and it's fair.

 

[DÛke]

...time to put it all together...

Here's the list of cards that are worthy enough so far:

Mental Fusion X1UU
Sorcery
Choose X cards in your hand, and remove the rest from the game.
Take an extra turn after this one.

Psychic Gravity 1U
Sorcery
Look at each opponent's hand and at the top 3 cards of each of their libraries.
Then look at the top 3 cards of your library and put them back in any order.

Ebb and Flow 3U
Instant
Target player returns 3 permanents he or she controls back to owner's hand.
Ebb and Flow costs 2 more to play for each Ebb and Flow card in your graveyard.

Odessa 3UU
Sorcery
Search target opponent's library for up to 4 non land cards and remove them from the game without revealing them to their owner.
"Don't get your hopes up..."

Mind Cage 2U
Enchantment
Your opponent's hand size limit is reduced by 2.
"Feeling a little stupid?"

Render with Illusion 1U
Instant
Creatures you control can't be the target of spells or abilities and are unblockable until end of the turn.
Render with Illusion costs you 2 more to play for each Render with Illusion card in your graveyard.

Lunar Bug U
Creature - Insect
As long as you have 2 or less lands, Lunar Bug gains +1/+0 and Flying.
1/1

Lunar Screen 1U
Instant
Counter target spell unless its caster pays an additional 2.
If you control 2 or less lands, Lunar Screen costs 1 less to play.
"As beautiful as it is, the moon offers such a wonderful...distraction..."

Lunar Fairy U
Creature - Fairy
Flying.
As long as you have more than 4 lands, Lunar Fairy gains +1/+0.
Tap: Add U to your mana pool. Play this ability only when you control 4 or less lands.
0/1

Lunar Sorcerer UU
Creature - Mage
U, Tap: Lunar Sorcerer deals 1 damage to target creature or player. If you have 4 or less lands, and you dealt the damage to a creature, you may tap that creature.
0/1

Morph U
Instant
Return target creature you control back to owner’s hand.
If that creature comes into play this turn, you may put a +1/+1 counter on it.

Psychic Warrior 2U
Creature – Warrior
All spells and abilities targeting Psychic Warrior resolve at the end of your next turn instead of any other time.
All damage dealt to Psychic Warrior is dealt to it at the end of your next turn instead of any other time.
2/1

Fading Traces 3UU
Sorcery
Look through target player's library.
You may remove from that library any cards, but only if each of those cards have no other copies of them in that library.
Shuffle that library.

Mercury Elemental 2UU
Creature - Elemental
Mercury Elemental also counts as an Artifact, a Land, and an Enchantment.
Mercury Elemental is unblockable unless the defending player pays 1 for each creature blocking Mercury Elemental.
3/4

Those are the neat cards, in my opinion. All been discussed and edited to almost perfection. I did increase the cost of Mercury Elemental, however, since it *is* a "Mercury" Elemental, I think it should be evasive. Providing that we already increased its cost by 1, I think the additional ability would set it just about right. Almost a perfect creature.

More cards later...

 

[Istanbul]

Mercury Elemental is strong as it is, but not broken. Thumbs up.

 

[DÛke]

...

Ok, good.

Few more card ideas...

Weaken Thought (U)
Instant
Until the end of the turn, your opponent's hand size limit is reduced by 3.

Psychic Phenomena (UU)
Instant
All damage dealt to any player and/or creature is dealt at the end of your next turn instead of any other time.
Spells resolve at the end of your next turn instead of any other time.

Time Confusion (UU)
Sorcery
During target player's next turn, his or her draw step is the last step he or she plays, his or her discard step is the first step played, and he or she skips his or her second main step.

Simplify (U)
Instant
Skip your next upkeep and discard step.

Notes on Time Conusion -- I'm not sure how playable it can be. It seems like an interesting idea...but maybe a dead one. The card probably needs rewording.

 

[Istanbul]

Duke...I will say this, all four of the cards are balanced. Trouble is...would you actually PLAY any of them in a deck? Would you actually devote any slots in your deck towards a card that ONLY prevents you from paying upkeep costs and discarding due to an above-7 hand size for one turn? Would you rather play Counterspell, or something that reverses upkeep and discard times, and denies someone only their second main phase?

Actually, upon further examination, Weaken could very easily be broken. I go first? I play an Island. Your turn. During your upkeep, I play Weaken. If you don't have any one-drops, you play your land, then discard three cards. I just paid U to make you discard three cards. Black never had it so good!

 

[DÛke]

...

Upon further examination, you should also notice that it becomes useless quite quickly. You basically, use it early or...you've got a dead card.

I agree that it's "unheard of" but hey...if it's not a first/second-turn play, you probably won't play it at all after that. I believe the card should be...a bit more powerful.

As for the other cards...I kinda agree, but not completely. Sometimes, coming up with "weak" ideas like that can lead to better and innovative discoveries.

I'll put more cards later...