Shambling mounds are temporary druid minion tanks, they are an improvement on the earth wall as they can actually move with the player. Like most minions and scale with class level and in this case they become more powerful with druid cast level.
A shambling mound made of earth, rocks, and dirt moves eerily here.
It's a big pile of dirt, rocks, and other earth clearly pulled up from the nearby ground. Hastily assembled by brute force using magic, it's not elegant, but serves well enough as a dumb minion in battle.
You insult shambling mound earth dirt.