Living Weed is a dangerous mob/biome/boss that will spawn if you make a Better than Beacons Nether Portal on top of Grass Blocks, and then attempt to destroy it AFTER entering the Portal, angering an Ironwood Tree, and then slaying it (By whatever means you do in that mod). The destruction of it will create a 10x10 biome that slowly spreads over time, simaler to The Taint. This biome does spawn in The Nether, however in a less hostile, non-growing version. Mobs, minibosses, and Defeat of The Weed below. But, before I get to that, may I mention that Living Weed grows hostile grass, and standing in Thick Grass causes 1 heart of damage per 2 seconds, and standing in normal grass will disable regeneration. (Tall grass grows only in the Overworld.)
Mobs 'n' Bosses[]
Nether[]
Hostile Pigman[]
Basically the title.
Sentient Terrain[]
An odd mob. It alternates between shapes, and is basically a random 20-block random-generated structure. It inches toward you, and should it touch you, it stops moving, and gives you Suffocation and Slowness. Only destroyable with whatever material it's made of; (e.g. a Dirt one would have low HP and only be damageable by a shovel; a Stone one would be a pickaxe; a Wood one only an axe).