[b]What is the terrain make-up of this world?[/b]
I like the idea of one main continent, maybe a second smaller one with several surrounding archipelagos. I think the idea that a continent sank is a bit out there. Though, it is not as far fetched if you take in the mythos of the Pacific Islanders in our would. However, too much contact and culture would be lost if that were to happen. Sure the merfolk would be happy, but it would be too easy to forget for the land locked races. I would like to see something akin to the collapse of Rome. A great empire lasting thousands of years as just fallen from within and out. Remaining factions find it too difficult to maintain the works of the Grand empire. Possibly tribal forces from the second lesser continent dealt the final blow but infighting weaken the united empire. Now this could set the stage for the larger factions. Each claim to be the rightful inheritor of "Rome". Lesser factions could be the smaller, more stable kingdoms that have tried to preserve their individual province or further raider tribes.

[b]What is the level of technology on this world?[/b]
I would like to see early, medieval level of tech akin to 5th, 6th, and 7th century Europe and asia.

[b]What creatures inhabit this world?[/b]
I am always partial to Humans. In every fantasy setting, i usually play a human. The only reason i never liked Lorrawyn block was that there was no humans. Elves and Merfolk would be good as well. Dwarfs are not unheard of in magic but they are not a lot. Vampires would also make up a good race, but more as power hungry nobles.

I can see Angels being present, but then Demons would also have to exist. I can only see them in smaller numbers because there is a relative balance between white and black mana on this world. Dragons i could see as a little more common because their intelligence and brute strength is useful in war.

[b]Does this world rely more heavily on certain colors of mana (such as innistrad being inherently more black)?[/b]
I do not feel that this plane should be color shifted like Innastrad. It would be interesting to see the plane temporary shifted towards red as all the colors of magic should be slightly more aggressive.

[b]Are we taking inspiration from any real-world sources?[/b]
The dark ages of Europe following the collapse of the Western half of the Roman empire

[b]Ally or enemy colors?[/b]
If there are to be five shard aligned factions, then there could easily make room for both ally and enemy color combinations. If we go with two continents, we could have each continent have five provinces. Each Province has its own terrain that would give rise to its own two color combination. Perhaps the main continent is home to the ally while the second has the enemy colors. The Greater Tricolor factions would have to navigate alliances through these provinces.

[b]Who's at war, and for what reason?[/b]
I admit i am bad with names so i will use the names of the ALara shards. 

Esper faction- Maintains the what parts of the empire that was not conquered and did not dissolve into chaos. However they lost the capital and had to flee to a more northern refuge. Their new capital is on a large island just off the mainland of the continent. They have almost undisputed control of the Northern frozen plains and swampland. They still govern themselves like the previous empire. This faction claims to be the proper remnants of the Empire and vowed to reclaim all lands lost during the collapse. This faction controls the most wealth.

Grixis faction- This faction holds onto the great desert waste in the middle of the larger continent. It also holds several mountainous island in the southern oceans. Their regions were more livable when the empire was intact, but they still hold onto it not willing to let anyone take it. Their naval fleet is second to none.

Jund Faction- These were the invaders from the second continent that forced the final collapse of the empire. They have seized large portions of the main continent for their own and wish to see all others fall under their control. They press hard against the Esper faction to prevent the empire rebirth. This faction has the largest land fortress.

Naya Faction - This faction has rallied the free Folk of its lands to throw off any attachment to the empire that oppressed them and resist the foreign invaders. They will not be ruled by anyone other than themselves. 

Bant Faction- This faction exists mainly on the second continent. Its rise to power pushed the Jund faction across the Sea to Topple the Empire on the main continent. This faction is preparing to launch a holy crusade across the sea

[b]And most importantly, what is this plane's name?[/b]
As I have stated before I am bad at names.