Minecraft has had a mod that gained tons of steam, and that mod is The Aether. Basically it's the anti-Nether. You make a portal out of glowstone and a bucket of water, and you will go the the Aether.
It just got released and I have to say I love it, but it has many problems. This build has a pretty much required inventory modder like TooManyItems. Diamond tools are crap in the Aether so it's a setup to start anew. you can
saddle flying pigs, but you only have one jump and a float down. You are tasked with finding and following the large peaceful Moas. Once they lay an egg, grab it and pop it in an incubator and wait for it to pop out a baby Moa. feed it poisonous Aechor Leaves to make it grow.
Zephyrs: These floating rectangular cloud things shoot ice balls at you and push you off islands.
Swets: These reskinned Slimes come in Blue and Gold versions. Blue ones jump on your head and ride you around while choking you, and Gold ones will pop you up into the air at first touch.
Cockatrice: These Moa-lookalikes come out when you get to the closest thing to night.
Sentries: These are the guardians of the Bronze dungeon and explode on contact.
Block with an eve?: The Bronze boss, he can only be hurt with a pick.
Valkries: These winged people are the guardians of the Silver dungeon, and are a neutral mob. However the medallions they drop are required for fighting the boss.
Valkrie Queen: The boss of the Silver Dungeon. Killed by any means.
Sun spirit: Gold dungeon boss. Lights you on fire at a touch, and he shoots lava balls, then an ice ball. Invincible by any other means then reflection. When he is killed, night is possible to fall in the Aether.
There's far too much to explain here. I'll just post the link to this mod.Clicky