hydrapack

This modpack will upgrade many minecraft structures including villages, mineshafts, nether fortresses, ocean monuments and more, adds a lot more structures you can explore for hours and find amazing loot. There are many new bosses for the player to defeat. The combat has also been upgraded adding new wepons and animation that make fighting a lot better. With the create mod you can make all kinds of machines and factories for anything you want. There are many new biomes too! The nether is a lot bigger and has many more structures, biomes and mobs!
After killing the warden, you can get it's heart that can be used to light up the portal in the ancient city to get to, the other side, an entirely new dimension with new mobs, new biomes and even 1 miniboss. 
There are many new bosses for you to fight that are some easier to beat and some harder with the hardest one being the wither storm.

Warning: This modpack requires a good PC to run properly with at least 16GB of RAM or higher and a good graphics card especially when runed with shaders, making giant create mechansims or fighting large mobs like the wither-storm
Note: Also, This modpack may show some warning on the startup with optifine but I have tested it and light doesnt appear in some blocks but it won't have any problems in your world.

Hope you have fun!