Got ninja'd before I could post this in a contest:
Karn's Spark
Confer (If you cast this card for its confer cost, it's an Aura spell with enchant planeswalker. It becomes a planeswalker again if it's not attached to a planeswalker.)
Create a 1/1 Myr artifact creature token.
Until end of turn, artifact creatures you control get +1/+1 for each artifact you control.
Enchanted planeswalker has ~'s loyalty abilities.


This one I actually posted
Ajani's Spark
Confer (If you cast this card for its confer cost, it's an Aura spell with enchant planeswalker. It becomes a planeswalker again if it's not attached to a planeswalker.)
You gain 1 life.
Create a 1/1 white Soldier creature token with lifelink. Put a +1/+1 counter on each creature you control that has lifelink.
Enchanted planeswalker has ~'s loyalty abilities.

Still think I should have went 1UUU on this one.

Regarding clutch of undeath, do you mean something like this?

2b
enchantment - aura
Enchanted creature gets +2/+2 as long as it has another aura attached to it. Otherwise, it gets -2/-2.

I meant more of
"Enchant permanent
if enchanted permanent is an artifact or enchantment- bad thing.
if enchanted permanent is a creature or walker- good thing."
Not necessarily black either. If it was black it would have to affect noncreatures indirectly. Like imposing a life payment or Nettlevine Blight-ing.

Yeah, something like Feedback / Warp Artifact, but maybe if you put it on a creature it gives you life instead

A round of Starstill reborn nominations.
Some pretty workhorse cards here, but they worked out all right.

I like the Espionage Owl and Heat Exhaustion, but Luminous Moth is quite weak for 3 mana. White has a plethora of small efficient flying white creatures that outclass this one at 2 mana. It is a Wind Drake at best, barring potential interactions with +1/+1 counters.

For the YMTC Pro Tour:
Round 1
-No entry-

Round 2


Round 3
Bear Trap Cannon
Artifact
: Attach another noncreature, nonequipment artifact you control to target creature. It gains "The creature this is attached to gets -X/-X, where is this artifact's converted mana cost". When ~ leaves the battlefield, sacrifice each artifact attached this way.
Boom, sh-clack clack!

This is what I should have submitted for PTYMTC round 3
Bear Trap Cannon
Artifact
: Attach another noncreature, nonequipment artifact you control to target creature. It gains "The creature this is attached to gets -1/-1" until ~ leaves the battlefield.
Boom, sh-clack clack!


Vicious Plague
Enchantment
When ~ enters the battlefield, put a -1/-1 counter on target creature.
Whenever a creature with a -1/-1 counter on it deals combat damage to a creature, put a -1/-1 counter on the creature damaged this way.

Hey that one's kinda cool. I like the flavor. Fun with persist, and is basically +1/+0 in combat with infect creatures.

80% somebody must have posted this card already somewhere. 20% it was me since I found the design in some old notes.
Should have called it Sorcerous Armaments Limitation Treaty and called the token "Treaty"

My round 4 PTYMTC entry:

Criteria was to modernize an old cycle or mechanic and I chose rampage.
"Killing Spree" was a bad choice of name, but otherwise I think the card was fine. Not spectacular but fine.


I also made this while working on the above.
Soul Of War
Creature - Avatar
Killing Spree X, where X is the number of creatures blocking this creature (Whenever this creature becomes blocked, it gets +X/+X until end of turn for each creature blocking it.)
Whenever ~ attacks, target creature must block it if able this turn.
5/5
-
Probably should have been a 4/4 with reduced cost. I feel that's the point where the opponent really has to wrestle with whether they should add a second blocker.

Tala, Light Of Unification
Legendary Creature - Angel
Flying, Double strike
Your split cards have fuse. (You may cast one or both halves of this card from your hand.)
Whenever you cast your second spell each turn, put a +1/+1 counter on ~ and draw a card.
3/3
-
I love the idea of granting fuse to split cards and figured commander was a good format to put the idea to use in. To get all the split cards it had to be . Then I just added some abilities that played nicely with playing split cards.



Hail To The Chief
Commanders cost less to cast
Commander creatures have haste.
Commander creatures get +2/+2.
-
To get players to play their commanders, that's why. Could be expanded into a cycle pretty easily.

Arms Training
Enchantment
Enchanted creatures you control get +1/+1.
Equipped creatures you control get +1/+1.


Combined Forces 1WW
Enchantment
Artifact creatures you control get +1/+1.
Enchantment creatures you control get +1/+1.
Planeswalker creatures you control get +1/+1.
Land creatures you control get +1/+1.
- Is there a proper order for listing card types?
- I just can't think of a better name at the moment. Strength In Versatility. Cross-Training could work, but only within a military theme.


Systematic Dismissal
Instant
Counter target spell.
~ costs less to cast if you control a creature.
~ costs less to cast if you control an artifact.
~ costs less to cast if you control an enchantment.
Baharaz turned the full weight of the Velnarian state against dissenters.


Secretary Of Labour
Creature
Tapped artifacts have no abilities.
2/2
"Each of your assembly plants puts on hundred good Ravnicans out on the streets! Where is the justice?"

I thought about giving Klajeth some way to power up through eating, but really, it already opens up a lot of possibilities. Sure, the treasure is way more valuable an ability, but gaining an ok sac outlet for creatures is something decks don't mind having. That, and if I tried to pretty it up by making it symmetrical with anything that triggered off sacing treasure, that ability would get nuts.

Turns out that the food type is restricted to artifacts. That means the previous iteration of Klajeth is nonfunctional. Here's a version that works, but gains some flavour wonk. Thanks to Q for he solution.
Klajeth, The Golden Glutton
Legendary Creature - Dragon
Flying
Other creatures you control are Food artifacts in addition to their other types and have ", ,Sacrifice this: You gain 3 life."
Noncreature artifacts you control are Treasure in addition to their other types and have ",Sacrifice this: Add one mana of any color."
4/4
"The name should have been a clue" - Bjoren Ill-fated.

This approaches the sort of thing I wanted to see in an Eldrazi vs Zendikar set.

Graypelt Battleground
Land
~ enters the battlefield tapped.
When ~ enters the battlefield, create a 0/1 colorless Eldrazi Spawn creature token. It has "Sacrifice this creature: Add ."
: Add .
: Add or . Use this ability only if you control no Spawn.

Should I make the Add ability "Use this ability only if you control a Spawn."? I'm worried that this land is already really dang good.

Gloryhound notice- I posted this after CotW went up. Just saying. Y'know cause there haven't been many nominations lately. Is why. For that reason. Only.