Name of this achievement is
Thresher Thrashed.
To get this achievement you have to complete the mission
You.Will.Die. (Seriously). This solution is going to be long, but it will say what you will need to defeat Terramorphous The Invincible (monsters name) as well as how to do it.
To get this achievement you have to talk to Tannis in Sanctuary
AFTER you finish The Talon of God.
EDIT: This is possible to do solo but it will be really hard, video posted at end of blog. Credit to Blaze VII for finding it. [End Edit]
Second EDIT: There is a glitch you can do it with 2 people, maybe more. You have to hide on a ledge basically the same as the glitch for Crawmerax. Video at end of solution. [End Edit]
Third Edit: You can start new game +, its like a playthrough two but makes a new auto save. Thanks to VampiricMist for this.[End Edit]
Beware, this monster is not intended to be fought alone, it was made to be fought against four level 50 characters with the most powerful weapons in the game. Its like the Crawmerax from the first game basically. To gain access you have to have 4 Eridium also and I'll give you some tips on how to defeat it.
- Its weak spot is its eyes, but it will take damage anywhere on its body just like every other creature.
- When the beam tentacles come out, kill them before they burn you.
- Flame resistant/immune shields are recommended.
- Spread out our you'll be group killed easily.
- Maya with Res is recommended.
- Don't stand to close to him.
How it attacks.
- With its tentacles by lashing out and pounding the ground up close.
- Burrows underground and comes up beneath you causing you to be thrown in the air, you shouldn't take damage but you may fall off the peak...which will make you die.
- There are 5 different types of tentacles, Spikes which shoot spikes at you. Beams which, well, its a laser beam. Rock tentacles which throw rocks at you, CANNOT be shot out of the air. Masher tentacles which mash you if you get to close. And finally Fire tentacles which throw fire at you.
- If you shoot at those tentacles and kill them, they won't cause any damage to the Terramorphous The Invincible.
- And when you piss it off it will be bathed in fire which takes reduced damage so just try and not die and wait till it calms down again.
After it dies you'll find a big amount of weapons with some orange ones (maybe). Just like Crawmerax....And when you leave the peak you'lll go through a chamber with treasure chests...loot boxes whatever you wish to call it.