Taller greener swamps. Leaves pile up creating the perfect environment for mushrooms, hydrangeas and cattails. Slimes also don't spawn in this biome, unlike the standard vanilla swampland biome.
Ground Cover: Grass
Plants: Hydrangea, Cattail, Mushroom, Vine, Lily Pads, Leaf Pile
Fauna: Sheep, Chicken, Cow
ExtrabiomesXL list of other biomes- https://github.com/ExtrabiomesXL/ExtrabiomesXL/wiki/List-of-Biomes