Terramorphous (A.K.A. Terramorphous the Invincible) is an end game raid boss in Borderlands 2
Terramorphous has many different types of tentacles, each with a different attack:
Strategy Guide and Tips and Tricks
You want to be level 50 (level cap) before fighting Terramorphous.
Watch for knockback. The fight takes place on a plateau and you don't want to get knocked off the plateau. You can take cover behind the various rocks that are scattered around. Also one side of the area has a cliff wall, so fight with your back to that wall so that you don't fall when you get knocked back. This won't keep you from dying, but it will keep you from getting knocked off.
If you do get knocked off, run back up to the top.
You should have the best gear, Epic and above.
Terramorphous the Invincible drops mediocre loot, often greens to purple, with one orange class mod dropping each time. Rarely drops the items, Teeth of Terramorphous (Shotgun), Breath of Terramorphous (Grenade Mod), Hide of Terramorphous (Sheild), or the Blood of Terramorphous (Relic).