Trigger: Kill all "An Earthen Mudwalker".
Phase One: Once the "An Earthen Mudwalker" are dead, "A Sludge Lurker" will spawn. When it reaches a certain point in its health, it will despawn, leaving behind 10 "A Muck Mudlet". These are mezzable and stunnable, and are best AE'd.
Phases Two to Six: Once the 10 "A Muck Mudlet" are dead, "A Sludge Lurker" will respawn. Again when it reaches a certain health, it will despawn, leaving behind 10 "A Muck Mudlet" yet again. This process will repeat for a total of up to 5 such waves, with each time the Sludge Lurker's health getting lower before it despawns, until on the last occassion, it will not despawn, but will finally die, and 4 "A Filth Gorger" will spawn back at the mud platform. These will immediately rush the raid.
Phase Seven: Kill the 4 "A Filth Gorger" to spawn the boss - "A Monstrous Mudwalker". He will immediately rush the raid on spawning. The Filth Gorgers are rootable and snareable.
The Boss: A Monstrous Mudwalker hits for 2k, rampages, and uses an AE root spell that will make aggro difficult. He is slowable. Because of the AE root, it is important that everyone attempt to cluster tight around him, to eliminate "ping-pong" aggro. During this fight, adds spawn on player deaths. These adds are mezzable, but do not despawn when A Monstrous Mudwalker dies.