Nidhogg

Nidhogg is a Behemoth in Death Dome. Nidhogg is the behemoth of the fourth district: Highway 66. He is a Behemoth, he has no weakness. He does very much damage at level 40 and with the full Singularity set equipped he kills you in two hits.

Defeating Nidhogg
Though it requires patience, there is a way to defeat Nidhogg: die, then use diamonds from the 5-day login bonus to revive. This will increase your damage and reduce the damage you take; assuming you know his attack signals, you can then dodge, parry, and block as needed.