Expandium

Expandium adds a lot of new content to Minecraft, including blocks, biomes, equipment, a new dimension, and changes to existing mechanics. It originally came from MCOL (which is why there’s a bunch of files labeled MCOL 1.7.4 and whatnot.

There’s hundreds of new blocks, including a ton of wood types (Jacaranda, Mahogany, Willow, Redwood, etc.), new stones (Limestone, Marble, and Blue Pearl Granite), minerals (Silver, Tin, Tungsten, etc.), and decorative materials.

Several new biomes have been added to the Overworld, including Redwood Forests, Willow Groves, Cypress Wetlands, Black Deserts, and Volcanic Highlands.

Each biome has its own terrain and vegetation. There’s also smaller additions scattered throughout the world, including bushes, twigs, rocks, and fallen driftwood.

Villages now can spawn with 2-4 houses or 20-30 houses. Larger villages have more buildings and resources, but I’ll leave the village overhaul to the other modders.

Expandium adds new tools, weapons, and armor (to name a few), using both vanilla and custom materials.

There are also new weapon types, such as spears, with their own equipment variants.

Your copper tools and armor even oxidize now!

Various changes have been made to existing Minecraft mechanics and recipes.

For example, stairs now craft eight instead of four, chainmail armor is craftable, and there are a few additional commands and inventory utilities.

Expandium also includes several experimental features, which are basically just Creative-only.

• Black Holes: Pull in nearby entities and blocks, tearing apart the surrounding terrain.
• Nukes: Powerful explosives with different yields, capable of leaving enormous craters.
• Meteors: Summon meteors that crash into the ground, causing explosions and leaving craters.
• Proximity to Sun: The proximityToSun gamerule controls extreme heat and cold. Positive values make the world hotter, while negative values make it colder, affecting the environment in different ways.
• Directional Gravity: Change the direction of gravity, allowing players to walk on walls or ceilings.
• Platforming Blocks: Various blocks for making parkour maps, including checkpoints, bounce pads, hazards, and timers.

Don’t want certain features? Most can be turned on or off in Expandium’s settings on the title screen.  
The settings are separated into categories like Biomes, Materials, Recipes, Terrain Generation, and Oddities

Especially for reading this entire description. Okay, you can go download now. Please.