MTG Salvation

Shrinking Wurm might be too cheap to micromorph. Is a possible 7/5 on turn three too much?

I'd like to suggest some changes...

Oath -- Whenever a creature WITH Oath enters the battlefield UNDER YOUR CONTROL, YOU MAY sacrifice [CARDNAME]. IF YOU DO, [EFFECT].

This sort of takes away the 'suicide vest' that was mentioned. It also takes the control of your board state away from your opponent.

I would suggest not calling the modes steps, as a step is part of a phase during a turn. Maybe another word could be used to keep clarification?

I'm almost positive the correct wording is "...twice as much damage instead" rather than "...double damage."

Shimmer would work I think. If Bounce or flicker aren't being considered.

In regards to your etb triggers...perhaps the reminder text should read "AS you cast a creature spell..." instead of when?

I feel 'Forget' would work better as a keyword for milling.

i.e.

Target player forgets two cards.
Forget the top card of your library.
Each player forgets a card.
Whenever a card is forgotten, [effect].
etc.

I actually use this in my custom designs and it works perfectly for me without ever changing any rules or how cards interact.

Everyone understands the concept of the round. Magic doesn't really use this idea even though it exists.

Here's the idea. The player who goes first has a large coin .Perhaps a poker chip or a Dealer button, though any coin would work. Establish which side is Day and which is Night.

The game begins in the Day. At the beginning of each of the first player's turns, the player flips the coin, changing it from Day to Night or from Night to Day. When the coin is flipped, is considered twilight.

Both keyworded abiities are static abilities.
"At twilight," is a triggered ability.

Diurnal -- During the day, [Effect].
Nocturnal -- During the night, [Effect].
At twilight, [Effect].

CARDS

Twilight Guardian 1W
Creature -- Human Soldier
When it becomes day, put a +1/+1 counter on Twilight Guardian.
1/1

Nightshadw Sage 2U
Creature -- Turtle Wizard
At twilight, draw a card if Nightshade Sage is tapped.
1/3

Twilight Zealot 1BB
Creature -- Zombie Cleric
Nocturnal -- During the night, Twilight Zealot has "T: Each opponent loses 1 life and you gain 1 life."

Duskvenom Spider 3GB
Creature -- Insect Spider
Diurnal -- During the day, Duskvenom Spider has deathtouch.
At twilight, destroy target tapped creature with flying.
2/4

Fiery Aurora 1R
Enchantment
At twilight, Fiery Aurora deals 1 damage to each player.

Oaken Shield of Dancing Twilight 1GG
Artifact -- Equipment
Equipped creature gets +4/+3 and has trample.
At twilight, attach Twilight Oak Plate to target creature with no equipment attached to it.
Equip 1GG

Midnight Chalice 3
Artifact
At twilight, you gain 1 life.

"You may pay 3 and reveal THIS from your hand. If you do, put it onto the battlefield tapped."? O.o

Crimson Sky Hunter I feel this should maybe cost an additional 1. Being that it's a 2/3 flier with both looting and life gain.
Shadows of Impurity The first mode might be too powerful for the price considering you can choose is twice.. Also, the last mode feels a bit weak even when chosen twice.
Fiery Retribution This is good. Just one minor nitpick, when referring to a life total or an amount of damage a numeral is used instead of spelling out the number. So, 'one' should be '1'.

It's important to note that rarity has no actual effect on a card's power level.

The reminder text should say "under his or her control" instead of "under your control" If your desired effect is a flicker. As it reads now, I can target your creature with it and if you pay the life, the creature would return under my control. I know it says he or she in the card text, but the reminder text doesn't but should.

Would be nice to see Reverse the Sands return again.
Or maybe this twisted version of it.

Drain the Sands 6BB
Sorcery
Each opponent loses life equal to half your life total rounded up. (Each of those players can't be reduced to less than 1 life this way.)

I like both of alwaysatoad's versions with flash.

And yes, I understand some may see it as implied, but it wasn't on the card as I read it, and the rules reminder of Bestow does not state the enchanted creature automatically gets the p/t.

I think Buy Time might be under costed. The pay 5 life and give away a creature probably would never be chosen except in extreme circumstances. Basically, I see this as a Murder for B.

Hour-Eater is intriguing.

Midnight Hour seems harsh. Works great in reanimate decks and with madness, etc. What if each player milled twelve?

No Escape is a textbook common. Good design, no changes needed. In essence it's a cheaper, flavorful black Arrest.

I REALLY like Time's Up. Very unique idea. Will there be more of this sort of effect?

Also, is there an overlying sub-theme of the number twelve?

As a creature, Blighted Eidolon's base p/t is -1/-1. No where on the card as is does it give -1/-1 or anything else to an enchanted creature when it's an enchantment. You put this on Birds of Paradise and you basically spent mana for no effect unless another permanent you control counts enchantments.