Steal Away
Tribal Sorcery — Rogue (R)
Prowl (You may cast this for its prowl cost if you dealt combat damage to a player this turn with a Rogue.)
Gain control of target creature with mana value less than or equal to the amount of combat damage dealt to it's controller this turn.

Flamekin Reveler

Creature - Elemental Shaman
Elemental spells you cast cost less to cast
Other shaman creatures you control get +1/+1
2/1

Might of Doran
Instant
Target creature gets +2/+2 until end of turn. If it is a Treefolk, it also gets +0/+2 and "This creature assigns combat damage based on its toughness instead of its power."
"No matter the state or name of this world, this forest will remain ours."

Incomprehensible Horde

Legendary Creature -- Elemental (R)
Vigilance, trample, haste
Elemental spells you cast cost less to cast
If an Elemental you control entering the battlefield causes a triggered ability of that permanent to trigger, that ability triggers an additional time.
5/5

Champion of Velis Vel
Creature — Shapeshifter
Changeling
Champion any number of creatures
: Champion of Velis Vel becomes a copy of a creature championed by Champion of Velis Vel, except it has changeling and its base power and toughness is X/X.
4/4

Velis Vel Grotto
Land (U)
: Add .
: Add one mana of any color among creatures you control.
Once a year, the crystals gleam with a glow commemorating every form a changeling has taken.

Alara

Tidehollow Behemoth
Artifact Creature - Beast (C)
Vigilance
[5/4]

(it's an archetype filler; not putting bells and whistles on it)

Dregscape Courier

Creature -- Human Rogue (C)
When Dregscape Courier deals combat damage to a player, draw a card.
Unearth (: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step or if it would leave the battlefield. Unearth only as a sorcery.)
2/2

Scourge of Sedraixs
Legendary Creature - Dragon Zombie
Flying
Devour 1
When ~ devours one or more non-Zombie non-Skeleton creatures, create that many 2/2 black Zombie creature tokens with decayed.
Even though it no longer needs to hunt, it still does. And with the necromantic energy of Grixis, what it eats starts to hunger as well.
[5/4]

Dragon's Feast

Sorcery (C)
Create two 1/1 red Goblin creature tokens with Prey 1 (They have "Whenever another creature enters the battlefield under your control, you may sacrifice this to put a +1/+1 counter on that creature.")

Dragon-Eater
Creature - Beast
Devour 1, Trample
Whenever ~ devours a creature with +1/+1 counters on it, put that many +1/+1 counters on ~.
[5/5]

Filigree Eater

Artifact Creature -- Beast (U)
Haste
Devour artifact 2 (As this enters the battlefield, you may sacrifice any number of artifacts. This creature enters the battlefield with twice that many +1/+1 counters on it.)
2/2

Maelstrom Borderpost
Artifact
~ is all colors.
You may pay and return a basic land you control to its owner's hand rather than pay Maelstrom Borderpost's cost. If you do, it enters the battlefield tapped.
: Add one mana of any color.

Strictly better than the original cycle in a few ways, but then again a lot of mana rocks are aside from the alt cost.

Flamemaw Peak
Land
Devour 3
: Add .
, Remove a +1/+1 counter from Flamemaw Peak: Add , , or . If this mana is spent to cast a creature spell, that creature spell gains haste and trample until end of turn.
All things are eaten on Jund. The only thing worthy to eat a dragon is Jund itself.

Next is Zendikar.

Grizzled Adventurer

Creature -- Human Ally (U)
When Grizzled Adventurer enters the battlefield, you may accept a quest. (If you do, abandon any other quests you have accepted.)
"I've still got some heroics left in me."
2/1

(Example Quest)

Slay the Scourge
Quest
Condition: A creature an opponent controls with power 4 or greater dies.
Reward: Create two Treasure tokens.

Dive Into Archives
Instant
~ costs less if you are famed (A player becomes famed when they complete a quest.)
Draw two cards.
"The codex we recovered from the sunken temple is not something we can easily part with."

Expedition Deserter

Creature -- Human Rogue (U)
You may cast this spell for by abandoning a quest you've accepted.
Deathtouch
Loyalty can be rented, but it can't be bought.
3/3

huh ... I was imagining quests to be like dungeons from the D&D set. Wonder what Libe's intention was?

Untimely Mist
Instant
Prevent all combat damage that would be dealt this turn. Quests can't be completed this turn.
"The fog is too thick right now for us to press onward safely. Let's set up camp, and hopefully we can continue in the morning."

Oh, good shout. I viewed them as enchantments that have a condition. Once completed, you get the reward and sacrifice it.