A Most Cacophonous Lure

A Most Cacophonous Lure is an optional mission exclusive to Commander Lillith & the Fight for Sanctuary in which you have to defeat Haderax the Invincible located in the Writhing Deep. The mission is given by Sir Hammerlock after the mission Paradise Found has been completed.

Background

 * "Sir Hammerlock has discovered a new and terrifying Pandoran monster that will almost certainly require four Vault Hunters cooperating to take it down, and one of those Vault Hunters is you! Below the thunders of the upper deep, the creature hath lain, in its undisturbed enormity. Yawn. Luckily, Sir Hammerlock knows just how to get it's attention"

Strategy

 * After activating the radio in the setup room of Writhing deep, Haderax will come out one of three geysers located around the arena and stand straight up with his weak spot on the back of his head, hidden from ground level.
 * He will spit a big acid ball at one of the Vault Hunters that leaves a pool causing corrosive damage over time before dissipating. After this Haderax will burrow back into one of the other two geysers while sending spikes that home slightly towards the Vault Hunters. Be sure to move away from your original spot while these spikes are coming, since they deal massive damage. The natural structures around the map make it easy to hide from these attacks. After the attack is finished Haderax will rise up from the third geyser and repeat the attack pattern. Every time Haderax comes out of or goes into the ground the other geysers will launch Vault Hunters standing on them into the air. Using this knowledge, one can predict on which location Haderax will pop up next.
 * While Haderax burrows into the ground the Vault Hunter must run to the other Geyser to launch him/herself up to a ledge which lets them shoot at his weak spot once he comes back up. After enough damage has been done Haderax will get staggered and lay with his mouth open on the natural structures. This might take a few loops to work. The Vault Hunters can now shoot another weak spot on the roof of his mouth to cause massive damage.
 * If Haderax isn't killed during the staggered phase, he will close his mouth and burrow back into the ground. Haderax will now start tunneling through the entire arena, doing damage to any Vault Hunters in his way and throwing spikes in different directions. During this phase he will restore a great portion of health lost from the previous fight. After this phase he will return to his first stance of burrowing and throwing acid and spikes. Haderax can be staggered multiple times until his health is depleted or the Vault Hunters are defeated.

Tips

 * The Geysers for a triangle around the arena. when planning to launch in the air The Vault Hunters should stand between the geysers on the opposite side of the geyser Haderax will rise from to get a greater chance of reaching the correct geyser before it no longer launches them. One could launch up while he is still rising up, but this will not guarantee he will come out of the right geyser later. This also leaves the Vault Hunter very vulnerable to the barrage of spikes, since there is no cover up there.
 * With at least 3 Vault Hunters, each one could be designated to a single geyser and survive until they need to get higher up. The other two should watch out Haderax rising and burrowing since this will still damage them.
 * An easier way to reach the geysers in time is to use the Toothpick Assault Riffle in combination with the Retainer Shield. This increases a Vault Hunters Movement Speed and Jump Height significantly while in Writhing Deep.  The shield also comes with Elemental Resistance to Corrosion. One can also add the Mouthwash Relic to increase the damage done by the Toothpick.
 * One can also void the geyser jumping entirely by using weapons with piercing and splitting projectiles like the Conference Call . This weapon allows you to shoot the weak spot on the back of his head from below, causing stagger without clear line of sight.