Make your own Magic card!

I'll finish the cycle. I'm not sure how balanced these are.

Mastery of White - WWWWWW
Legendary Enchantment
If you control a land that can tap for any color of mana other than white, sacrifice ~.
At the beginning of your upkeep, you gain 2 life.
XW: Choose one - Up to X target white creatures gain protection from a color of your choice until end of turn, or put a +1/+1 counter on up to X target white creatures, or put X 1/1 white Soldier creature tokens onto the battlefield.

Mastery of Red - RRRRRR
Legendary Enchantment
If you control a land that can tap for any color of mana other than red, sacrifice ~.
At the beginning of your upkeep, you may discard a card. If you do, draw a card.
XR: Choose one - ~ deals X damage to target opponent and up to one target creature that player controls, or destroy target artifact with converted mana cost X or less, or red creatures you control get +X/+0 until end of turn.

edited 20th Aug '14 8:37:10 PM by videogmer314

I can imagine what would happen if they were ever printed. Vedalken Plotter would become a must-have sideboard card.

Or any of these cards.

edited 20th Aug '14 8:49:04 PM by videogmer314

Or those too.

I would suggest changing the first ability to something like "If at any time you have (insert other colors) mana in your mana pool, sacrifice ~", since I don't think the rules allow cards to do things based on what other cards might do.

Also, does colorless count as a color for the purposes of these cards?

First, Reflecting Pool seems to indicate otherwise.

Second, it doesn't count as a color in any other context (for example, Gods Willing can't give protection from colorless), so I would assume no.

Strike up the Band 2RR
Enchantment
All players in this game must sing everything they say. Whenever a player doesn't, any player may pay R to deal 1 damage to that player.

edited 20th Aug '14 10:09:00 PM by TheSpaceJawa

Rchekk Krol, Hivemaster (WUBRG)
Planeswalker - Rchekk
5
+1: Put a 1/1 colourless Sliver creature token onto the battlefield under your control.
0: ~ becomes a Sliver creature with power and toughness equal to the number of Slivers you control until end of turn. Prevent all damage that would be dealt to ~ while it's a creature. This effect lasts until the beginning of the next end step.
-8: You get an emblem with "Sliver creatures you control have "Whenever this creature attacks, put a 1/1 colourless Sliver token onto the battlefield tapped and attacking.""

Inspired by Maro talking about the possibility of non-humanoid planeswalkers on Blogatog. Probably terrible but at least it feels like a sliver.

Grog the Reckless 3R
Planeswalker - Grog
+1: Put a 1/1 red goblin creature onto the battlefield.
-2: Goblin creatures you control have haste, trample and +1/+0.
-5: You get an emblem with "If you sacrifice a goblin, return it to the battlefield with a +1/+1 counter."
Loyalty: 2

Irokk, Planeswalker (WUBRG)
Planeswalker - Irokk
All slivers are planeswalkers in addition to their other types with the same abilities as Irokk.
+1: Slivers get +1/+0 until end of turn.
+1: Slivers get +0/+1 until end of turn.
-8: You get an emblem with "Slivers have +3/+3 and have flying." Three slivers must activate this ability in a turn for it to have any effect. It only occurs once per three activations.
Loyalty: 3

edited 21st Aug '14 8:04:52 AM by ImperialSunlight

We should be really, really glad that Slivers can't become planeswalkers...

Of course, now that they're humanoid and seem to be building societies...

Now all we need is an unhinged Planeswalker.

Mox Gleemax Garfield, Perfect Realization of the Lotus - ∞
Planeswalker - Gleemax
You choose all targets for all spells and abilities, and all blockers.
+10000: Add one thousand mana in any combination of colors to your mana pool.
-15000: Declare a card name. Put a token that's a copy of that card onto the battlefield under your control.
-1,000,000: You win the game.
Starting Loyalty: 1
When the twisted experiment concluded, R&D thought they had succeeded. As Gleexmax would later tell them, they were right.

Still relevant :P (reposting mostly because I really like my drawback)

I have a feeling I don't really know what I'm doing with this first one. :/ Anyhow, it's Linkin Park Time!

Build it Up 1W
Instant
Put a +1/+1 counter on target Wall you control.
Storm
--Fuse--
Burn it Down 1R
Instant
Burn it Down deals 1 damage to target creature an opponent controls. If it cannot, instead it deals 1 damage to target opponent.
Storm

Lost in the Echo WW
Instant
Copies of spells cannot be put onto the stack this turn.

Castle of Glass 4
Artifact
Blocking creatures you control are indestructible.
When you are dealt combat damage, sacrifice Castle of Glass.

Victimize 1B
Sorcery
Target opponent chooses a creature he or she controls and puts a -1/-1 counter on that creature for each land he or she controls.

Bag of Bones 3B
Creature - Zombie Horror
Whenever Bag of Bones attacks, it gets -1/+1 until end of turn.
Whenever Bag of Bones blocks, it gets +1/-1 until end of turn.
It writhes and crawls in endless discomfort, its skin continuously crawling the other way.
3/3

EDIT: Fail; forgot P/T for the Bag. EDIT 2: And nerfed it a bit.

edited 23rd Aug '14 12:16:24 AM by Knowlessman

Top-down:

Blade Lock (1W)
Enchantment
Prevent all damage that would be dealt to each creature by creatures with equal power to it.

Parry and Riposte (1W)
Instant
Prevent the next 3 damage that would be dealt to target blocking creature this turn. It gains last strike until end of turn.

Victimize is already a card btw.

The Dark Eternal Night 4BB
World Enchantment
At the beginning of each player's upkeep, that player discards a card, sacrifices a creature and loses 10 life. Any player may pay 4B to avoid this effect each turn. (I'm not exactly sure how this is meant to be worded. Not like this, I'm sure)
Madness 4B
Trapped in a hellish dream
Spinning past worlds unseen...

Victim Ice (B)
Instant
Destroy target snow creature.
"Try a pun like that again and I will pump so much ice magic into your tongue that it will fall off." - Heidar, rimewind master

Encasing Iceberg (XU)
Creature - Wall
Defender
When ~ enters the battlefield, exile target creature with toughness X or less until ~ leaves the battlefield.
If a red noncreature source would deal damage to you or a creature you control, instead sacrifice ~.
0/X

edited 23rd Aug '14 12:20:54 PM by IrishZombie

Might want to make that one XWU instead since I am pretty sure that Oblivion Ring effects aren't in Blue's color pie, even though the flavor certainly fits.

I wonder, would it fit blue's color pie if the guy controlling the exiled dude gains control of the iceberg? That way, it's less of an O-Ring, and more of a reversible Polymorph.

Hmmm... that might work actually. I don't remember that sort of effect ever having been put on a card before, at least not after the stricter color pie rules were a thing.

Okay, then. New version:

Encasing Iceberg (XU)
Creature - Wall
Defender
When ~ enters the battlefield, exile target creature target player controls with toughness X until ~ leaves the battlefield. That player gains control of ~.
If a red noncreature source would deal damage to a creature or player, instead sacrifice ~.
0/X

Gift of Bolas (5)
Artifact
~ enters the battlefield with three scheme counters on it.
2, T, Remove a scheme counter: Choose one - Copy target instant or sorcery spell, and you may choose new targets for the copy; or target player loses 3 life; or untap target permanent and gain control of it until end of turn.
At the beginning of each end step, if ~ has no scheme counters on it, you lose the game.
"Some find it amusing to play the servant when granting favours. I find it tedious. Prove yourself useful or I will pick my teeth with your bones." - Nicol Bolas

So... remove the last scheme counter, then give it away to make an opponent lose? Seems fair.