One of the ideas central to Zendikar is that it has a lot of priceless artifacts* and other items of power hidden away in dangerous places. In the cards, the enchantment card type was used to represent a band of adventurers going on a quest to find one of these. The most direct example is Quest for the Holy Relic .
As we are a band of adventurers going on a quest, I think we should look to these 'quest' cards for inspiration. There are 19 of them.
The original reason for the existence of artifacts was that long ago on Dominaria there was an empire ruled by a race of human artificers called the Thran, who, after their fall, left powerful ancient artifacts scattered across the plane. MtG now shifts planes every year, and most of the time there isn't a good flavour reason why artifact cards exist. I believe Zendikar has the best justification for the existence of artifact cards (apart from Dominaria and the artifical plane of Mirrodin, that is).
I've already looked at Quests as adventure hooks for my campaign (twisted, of course), but Ascensions have just hit my Will defense and knocked me prone in amazement.
S P O I L E R S A L E R T ! ! !
In the original story, the Eldrazi break free from their prison because some dark prophecy/planeswalkers safeguard that Jace, Chandra and Sarkhan activated at being together in the Eye of Ugin (a location, not an actual body part of someone/something).
So it just came to me: this prophecy may revolve around the heroes' ascensions instead of three planeswalkers. This "coming" of a Luminarch, an Archmage, a Bloodchief, a Pyromancer and/or a Beastmaster may trigger the Eldrazi's freedom.
Now that I re-read it, there's not much of a sopiler in here... the events described all happen in a webcomic series: Awakenings and Enter the Eldrazi.
"No curse we can't reverse; no spell we can't break; no demon we can't exterminate; no plane we can't reach"
- Motto of the Magnificent Order of the Planeswalkers, as said by the first time by Veritatis, its founder and the Grimmchester Brothers mentor
The Eldrazi breakout actually has two parts - though the first part gives no indication that it is incomplete.
Part One: The Eye of Ugin is unlocked by three planeswalkers accidently fulfulling the lock's 'combination', letting out the Eldrazi, but not the Eldrazi Titans. The combination was three planeswalkers (Sorin, Ugin, the Lithomancer), one of whom is a dragon (Ugin), and the casting of the colourless fire spell Ghostfire , a spell known only to Ugin and a few others. The combination was fulfulled by three planeswlakers (Jace, Chandra, Sarkhan), one of whom was in dragon form (Sarkhan), and the casting of Ghostfire, whose existence was discovered by the combination of Jace's brains and Chandra's fire talents.
Part Two: Nissa, against Sorin's advice, destroys the Eye of Ugin, letting out the Eldrazi Titans in the hopes that this will allow the Eldrazi to leave Zendikar. Unfortunatly, the Eldrazi are still unable to leave the plane, and begin destroying it. In the Teeth of Akoum ends at this point, so we don't have any offical information on how effective the Worldwake is at fighting the Eldrazi. Personally, in EDH games, I've actually held non-Titan Eldrazi at bay with Worldwake cards like Avenger of Zendikar , Goliath Sphinx , and even taken down Kozilek with Novablast Wurm .
Teeth seems to indicate that there is actually a third part to the Eldrazi's imprisonment, a safeguard that prevents them from escaping from Zendikar into their home, the Blind Eternities. If you're keen on doing something with the Ascensions, perhaps it could be a high-level adventure trying to break open this final lock and force the Eldrazi to leave Zendikar.
Ior Ruin Expedition - Akoum here is only one reliable source of blue mana on Akoum - a huge hexagonal lake called Glasspool. The water is eerily calm, not shifting even when roil quakes shake the surrounding lands. The lake is deep, but due to it's stillness and clarity, if you stands on a nearby mountain peak, you can see all the way down to the lake's bed, where there is a ruin site known as Ior. Ior is belived to have once been a center for magical learning, and some speculate that powerful magical artifacts still lie at the bottom of Glasspool today. Glasspool is home to a number of aqautic drakes.
Soul Stair Expedition - Ondu The Prison of Omnath is a high mesa thought to be the prison of an incredibly powerful mana-elemental named Omnath . The mesa-top is ringed by a circle of hedrons, globular swamp-growths, and animal bones. A pit in the center leads to the Soul Stair, a winding spiral stircase that leads down into the depths of the earth...and to Omnath.
Quest for Pure Flame - Murasa Murasa is ringed by a mountain range known as the Wall. Glint Pass is a network of underground caverns that stretches under the Wall. The coastal entrance to Glint Pass is huge sea cave, accessible only for a short time at low tide. It is one of lonly four ways to cross the wall - provided you can get through the sea cave before the tide rises, and provided you can find your way through the labyrinthine maze of booby-trapped tunnels , fire-quartz lit caverns, and magma rivers. Glint Pass is home to an unknown number of vampires, who live in the hidden underground city of Visimal, but will sometimes hire themselves out as guides to travelers through the caverns. Also hidden within Glint Pass is the fabled Cypher in Flames, a magical burning glyph said to have incredible powers related to both pyromancy and teleportation magic.
These are really good, guys. Thanks for putting them up here. An interesting place I've always wanted to begin a session from was combat. As soon as all the players meet, something happens and there's a fight. Barfight, drake attack, major goblin incursion, whatever. I think it could be fun. Combat tends to catalyze people into action. Let's say, for example, Chadir the Navigator is rumored to have found an extremely old map that hints at something deep in the heart of Glasspool. He's sending representatives around Affa to round up people for an expedition, and of course, Sachir hears about it. Sore that he's not asked to participate in the trip (Chadir is shrewd, knows that Sachir will end up taking it all for himself), the leader of the Akoum Expeditionary House orders all of the representatives of Chadir to be arrested. It ain't easy, though, taking on an explorer, and a fight breaks out. How does that sound for a beginning? Vyasar