Steam-village: The steam-punk world of tomorrow, TODAY! Floating in the sky. There are two forms of these: Blimps and Sky castles.
Sky castles are massive castles made of stone brick and such floating in the sky. This place is typically non-hostile and populated by villagers. You can find loot here, but nothing of incredible value. The biggest thing you can find here, is the replacement elytras and sky-beds.
Replacement elytras are just Elytras, but slightly less durability, just in-case yours breaks.
Sky-beds are how you sleep in the sky. There IS a day/night cycle here which works like the overworld's. Only night here only lasts a quarter of each day, as opposed to half of it.
The other type of village is a Blimp-base. This is typically one or two blimps suspended in the sky with villagers in it, no big deal.
There are typically 3 biomes which offer no additional adversity to you:
Clouds: Which are just clouds. You can walk on them, but you will eventually fall through. On the contrary, the darker the cloud the longer it takes to fall through it. All the clouds in a biome work on a timer, where they will eventually turn dark-grey. When dark-grey they are thunder-clouds and will electrocute the player occasionally if they're standing on them. When clouds are thunder-clouds, players will not fall through them.
Winds: These are more of a super common structure, as these winds will push you up, down or a cardinal direction if you glide into them on an Elytra. It's super useful for getting from island to island.
Sky-Islands: there are actually whole giant island in the sky with their own ores, sky-dirt (just normal dirt but bluer) , sky stone(stone that's more blue), sky trees/wood (blue again), and sky-fruit which nourishes one back to full hunger almost instantly, but doesn't give much saturation.
Storms: There are areas of the world where gusts of wind have accumulated. This is hell for Elytras which just get blown everywhere, but pegasuses can fly through them with no problem.
There are 3 biomes you want to stay clear of.
Ozone layers: These areas are toxic to your health and will cause one to breathe as though they are underwater, but more importantly, they contain smog creatures which will float into you and cause poison effect.
Storm Dungeons: There are areas where one can find massive permanently-dark storm clouds. These cloud blocks are permanently thunder-clouds and thus the electric bit stays in focus. Likewise, there's plenty of angry mobs in here to cause trouble too. In the center of these you can sometimes find a boss-griffen which will slash at you and fly after you. It is passive however and will only attack if provoked. Drops golden feathers.
Dark-Castles: Like villager castles, only the loot is better and instead of helpful villagers, you're greeted with a barade of evil monster to slay you.
You can find these randomly, although they are typically not a good thing to find.
Ufos: RARELY you can find a mothership which contains hostile aliens with blaster that work like bows. If you kill an alien you can sometimes get it's blaster. The blasters have 3 settings-flame (sets target on fire) -mark (causes target to glow) and -obliterate: Causes target to explode (Note, aliens will not use this mode, only flame and mark). These blasters can be enchanted to become unbreakable, or get looting, but not much else. The rest of the ship is pretty standard, the hull is made of unbreakable "alientium" blocks. In the center of the ship you can find a netherstar power core.
A netherstar power core is essentially an infinite power source for anything that needs power. It's crafted with 3 diamonds in a row, 3 nether stars in a row, and 3 redstone devices (repeaters/comparators) at the bottom.
The best use for this core however, is the docking bay. The bay is in another part of the ship and it contains scouter-vesicles. These vesicles work like minecarts, only they float when powered with heat or a netherstar power-core, and without power they run across water like boats, or on tracks like minecarts. These are essentially the best ways to fly, but you need Alientium to craft it. And sadly, that's an unbreakable block.
God-temples: The main boss for this place is to kill the Sun and Moon gods respectively. There are temples you can find for each god made of sun-godium and moon-godium. The sun god can only be killed at night, and the moon god can only be killed during the day.
The moon god will attack you with water attacks and gravitational pulls. Likewise, it spawns in minions to do it's main dirty work (skellitons, zombies, creepers ect.) by killing the moon god you get 3 rewards:
-The moon: You now hold the moon in your hands (it will disappear from the sky) it's basically a trophy, but you can use it again to re-spawn the moon-god (putting the moon back).
-Half the god-crest item
-A random armor peice of Moonantium. Moonantium is indestructible and comes with specific changes that benefit the player like a low-grav toggle or an effect that knocks away attackers. Likewise, this armor piece can occasionally be a moon sheild which when equipped causes enemies that need dark to spawn to not notice you. (So things like zombies and creepers will ignore you, but blazes and smogs will not. )
The sun-god is essentially the same but resides in a sun temple. Likewise it will burn you and suffocate you. You'll want to have an aqua affinity enchantment to help you here. It won't summon bad-guys however.
Killing it will earn you the other half of the God-Crest item, as well as the sun, which causes eternal night time in any dimension (DO NOT USE BEDS) but can be used as a trophy, OR an infinite power source.
The real benefit of killing the sun god is the sun-sword. It can be used as a hoe, a stronger-then-diamond sword, and it's also offers fire-protection, and evaporates water when you crouch with it.
The god-crest is use to fight "The truth" . Craft the 2 peices of the crest together to get the God.exe crest. This will act as a map, sending you to a specific place:
The Origin point.
This is a 3x3x3 block that looks like gold. You will need to place both the actual sun and moon onto the pedestals here. Doing so will spawn the Red-moon.
The red moon is essentially the worst boss ever. Simply survive a total of 3 days while EVERYTHING spawns enemies ALL the time. This should be easy with your armor and sword.
Once it's done, the 3x3x3 blocks of previously unbreakable gold will disappear revealing the center block: Creation.
Place this block in a crafting table and it will teleport you to the final boss which is actually somewhere in the Deep End, but was surrounded in bedrock. Inside, text will appear everywhere as the boss attacks you. You'll be able to tell his attacks like this:
-Potion tag effect ect
and other things like this. The final attack when the boss is almost dead will be /kill. Which will instantly-kill you. To activate this command however, the boss must first reach the "Enter" key which has appeared in the center of the arena. Protect that key! Kill the boss before he can hit the key, and you win.