A plane that no longer moves. One side is completely frozen and the other is a hellish wasteland where the sun never sets.

Card Type Matters (not subtype, I'm talking the stuff Tarmogoyf cares about)

Criteria: Black common Seal of___ style card. An enchantment that does nothing when it enters the battlefield, but can be sacrificed to produce an effect. Thinking we could use a cycle of these, but it doesn't have to have any real connection to the others.

In every set enchantments are the least common card type (well next to walker). We probably want to bump the numbers up a little bit for Starstill, but enchantments are still the key to completing mastery and shouldn't be too easy to draft. I don't want it to be hard to draft an enchantment deck, but I don't want people doing it by accident either.
For this set we probably want 2 common enchantments in every colour. Maybe one in some colours. I'd like to get a cycle of seals in at common or uncommon (I like the tension between saccing them for an effect and losing mastery).

Seal Of Piety
Enchantment
Sacrifice Seal of Piety: Target creature gains indestructible until end of turn.
Who would harm those without sin?

Ace of Moxes, although TPzombieW's should be in the set too.

Seal of Churned Earth
Enchantment (c)
Sacrifice ~ : Return target creature card from your graveyard to your hand.

In every set? Theros is an obvious aberration in favor of enchantments, so we'll disregard that. But Gatecrash had Enchantments-Artifacts-Lands as 26-13-11. RtR was 29-12-13 (excluding basics). AVR was 31-14-10. INN was 29-22-12. M14 was 28-23-3.

It seems to me, in every large set in the past 3 years, enchantments are the second most common permanent type after creatures.

I don't think this is a top-down set or a bottom-up set; I think it's both at the same time. But if I had to pick one, it would be a bottom-up set. I think we've put more work into the mechanics of this set than the flavor so far. And the reason is because Card Type Matters is such an ingenious theme for a set.

The poster who came up with that theme was TPzombieW. So when he makes a post about mechanics, I tend to listen closely to whatever he says.

-Yeah, I totally ripped off Steinhauser's red seal here. I just looked at it and thought, "wow, that's a great design for a seal, but red doesn't do its looting like that".

Actually, why is our equator named after that RGW legendary creature?

Seal of Lost Traces
Enchantment
Sacrifice ~: Return target permanent you control to its owner's hand.
The first thing an apostle leaves behind is the way to return.

Seal of Arcane Currents
Enchantment
Sacrifice ~: Instant and sorcery spells you cast cost less to cast this turn.
Many trader routes are chosen for reasons alien to all but the most esoteric of merchants.

Seal of Crushing Sands
Enchantment
Sacrifice ~: ~ deals 4 damage to a creature target opponent controls of his or her choice.
Viashino tribes gives their prey the freedom to choose their own demise, even if it's usually done unknowingly.

Seal of Flourishing Blossoms
Enchantment
Sacrifice ~: Put two +1/+1 counters on each creature you control that entered the battlefield this turn.
Sages still ponder to this day how there are seasons in Maraka.

I like the "seal of [adjective element]" name theme, so I'll go with that.


Seal of Blazing Sun
Enchantment (C)
Sacrifice ~: Destroy target attacking or blocking creature.
I see thee by the light of day.
Begone, evil! Go away!

Seal of Frigid Winds
Enchantment (C)
Sacrifice ~: Tap up to two target creatures. They don't untap during their controller's next untap step.
Cower, huddle; the cold wind blows.
You should have worn some warmer clothes.

Seal of Churned Earth
A second life, just like the first
Except you smell a little worse.

Seal of Secret Fortunes
Enchantment (C)
Sacrifice ~, discard a card: Draw two cards.
Would you risk your worldly stores
In pursuit of a little more?

Seal of Wild Beasts
Enchantment (C)
Sacrifice ~: Put a 2/2 green Wolf creature token onto the battlefield.
Teeth, claws, furry hackles,
I release you from your shackles.

Seal of Nature
Enchantment
Sacrifice [cardname]: Each opponent sacrifices an artifact or enchantment.
"Marath tolerates none of your foolishness."

Seal of Sandscouts
Enchantment
Sacrifice [cardname]: Put two 1/1 red Viashino scout creature tokens onto the battlefield.
Viashino scouts watch travelers in Illpyre, waiting weeks for the perfect moment to strike.

Seal of Annulment
Enchantment
Sacrifice [cardname]: Counter target artifact or enchantment spell unless its controller pays

Seal of Mirage's Skill
Enchantment
Sacrifice [cardname]: Exile target creature you control, then return it to the battlefield under your control.
(white-culture) tracker have learned to hide like mirages.

Seal of Warding
Enchantment
Sacrifice ~: target creature gains protection from the card type of your choice until end of turn.

Seal of Disruption
Enchantment
Sacrifice ~: counter target spell unless its controller pays .

Seal of Rage
Enchantment
Sacrifice ~: target creature gets +1/+0 and gains first strike and haste until end of turn.

Seal of Sprouting
Enchantment
Sacrifice ~: target land becomes a 4/4 green Elemental creature until end of turn. It's still a land.

In this cycle, they all target creatures (or creature cards).

Seal of Determination --
Enchantment (C)

Sacrifice Seal of Determination: Target creature gains vigilance until the end of turn.

The heat, the cold can't be ignored,
but use the other to be cured.

==xx==

Seal of Mist --
Enchantment (C)

Sacrifice Seal of Mist: Target creature can't be blocked this turn.

To pass through ice, and frost and rock;
First, get blessing through Glacinorak

==xx==

Seal of Churned Earth --
Enchantment (C)

Sacrifice Seal of Churned Earth: Return target creature card from your graveyard to your hand.

To rot, a body must be torn by earth.
But earth remembers, and grants rebirth.

==xx==

Seal of Desire --
Enchantment (C)

Sacrifice Seal of Desire: Gain control of target creature until the end of turn. It has haste and can only attack or block alone this turn.

The heart knows, the brain wants, the body does.
Hearts break, brains wane, the body lusts.

==xx==

Seal of Contest --
Enchantment (C)

Sacrifice Seal of Contest: Target creature you control fights target creature you don't control.

Animals fight with body, men fight with steel;
remove the advantage to make them fight equal.

Seal of Existance
Enchantment (U)
Sacrifice ~: Exile target attacking or blocking creature.
The ties that bind
The ties that blind
Know that this aggression
Is your last transgression

Seal of Frozen Exhaustion
Enchantment (U)
Sacrifice ~: Tap all creatures your opponent controls.
There are times when the cold feels warm,
Even the most jagged of rocks offer the invitation of comfort,
Sleep as the cold demands for you have been sworn

Seal of Volcanism
Enchantment (R)
Sacrifice ~: sacrifice a mountain, destroy up to two target lands.
Insert

Seal of Terraformic Growth
Enchantment (C)
Sacrifice ~: search your library for a basic land card. Reveal it and put it into your hand. Then shuffle your library.
Insert

Seal of Endurance
Sacrifice ~: Untap target creature. That creature gets +1/+1 until end of turn.
-Kind of want a white seal you'd rather keep to fuel enchantment strategies than one you want to sac for effect.

Seal of Knowledge
Sacrifice ~: Discard a card then draw two cards.
-Yeah, I totally ripped off Steinhauser's red seal here. I just looked at it and thought, "wow, that's a great design for a seal, but red doesn't do its looting like that". I'm not too worried about players potentially dodging the discard condition by waiting until they have an empty hand. It probably means they had to sit on the seal for a few turns without it doing anything.

Seal of ___
Sacrifice ~: Until end of turn, if an instant or sorcery source you control would deal damage to a creature or player, it deals that much damage plus 1 to that creature or player instead.
Tempted to do a burn spell-as-seal card, but let's give the instant archetype all the burn it can get. I see "ton of spells at once" being a red archetype.

Green:
Reprint Seal of Primordium
Preferred in decks that don't care about the early game as much. With counting permanents on the board being a mechanic, we probably want games o go slightly long.

OK, final touch-ups (renamed Permission to a -tion word; mocking-up of the rename of churned earth, adding parallel flavor text.)

Seal of Eradication
Enchantment (C)
Sacrifice ~ : Exile target enchantment.
That which should have never been / Is banished, nevermore be seen.

Seal of Revocation
Enchantment (C)
Sacrifice ~ : Counter target instant spell.
That which should not be allowed / Is voided, dispersed into cloud.

Seal of Exhumation
Enchantment (C)
Sacrifice ~ : Return target creature card from your graveyard to your hand.
That which once had walked the land / Is given one more chance to stand.

Seal of Demolition
Enchantment (C)
Sacrifice ~ : Destroy target artifact.
That which formed in brass or steel / Is crushed as insect under heel.

Seal of Exploration
Enchantment (C)
Sacrifice ~ : You may put a land card from your hand onto the battlefield.
That which was unmapped domain / Is now forever under reign.