Welcome to the World Gen Mod!
It adds sixteen biomes (so far), five new random stones, a new dimension that only features the modded biomes, a new mob, and a new fluid, Oil. (Not sure if Oil works, but please tell me if it doesn't!)
By the way, you should probably use the latest 1.15.2 forge for this mod.
New Biomes + New Dimension:
Dirty Plains - It's like the plains, but instead of Grass, you'll find lots of Podzol.
Fertile Desert - It's like a desert, but with more grass and trees. You'll find lots of donkeys here.
Arctic and Antarctic - Cold. Lots of polar bears in both.
Fungal Forest - Imagine a Mushroom Biome with more Mushroom.
Crimson Plains - Very very red. A new wood type lives here.
Obsidian Shards - A very rare biome that is filled with lava and Obsidian. Could be laggy, so stay away if your computer is weak.
Desert Mountains - Mountains in the desert, what more can I say?
Limestone Valley - A big valley filled with Limestone.
Flatlands - A very flat, grassy area. Great for building!
Deep Forest - Filled with lots of foliage. Hard to get through.
Mineral Mountain - A mountain filled with Shale and Gabbro.
Mega Mountain - A huge mountain. Goes up to the build limit.
The Pit - Dangerous.
Melted Antarctic - 99% Water and Fish.
Dirty Stone Mountains - It's like a mountain, but dirtier and shorter.
Extreme Dimension - A dimension with only the modded biomes in it. Good for looking at the mod!
New Blocks:
Chalk (Block) - Nice to look at. Mine it to get Chalk (Item)!
Chalk (Item) - Can be used to make Whitestone.
Mahogany Logs, Wood and Planks - A new, very red wood. Found in the Crimson Plains.
Gabbro - A hard rock that's found deep underground.
Tin Ore - Used to make Tin Foil (no uses yet,) and Tin tools.
Whitestone - Purely aesthetic. Can be polished and turned into bricks.
Shale - Made of lots of flat planes of rock. Useless for now.
Limestone - Strangely, more yellow than lime. Found mostly in the Limestone Valley
Oil Holder - Holds Oil. (Probably?)
Dirty Stone and Cobblestone - Stone and Cobblestone but dirty. Found in the Dirty Plains.
Slush - Slushy.
New Mob(s):
Pest - Silverfish but worse. Looks like Gabbro.
New Fluid:
Oil - Can be used as fuel.