Calamity is an Elite Boss enemy from Arachnos. He has been sent by Lord Recluse to test the loyalty of villains helping to overthrow President Marchand.
Villains can find him on the Prove your Dedication mission during the Mender Tesseract Strike Force.
Mu Guardians pulse with the blood of their slaughtered ancestors in their veins. They have read unholy tomes, visited other planes of existence and performed dark sacrifices too terrible to mention to become the masters of the mystic arts.
From the second mission of the Mender Tesseract Strike Force:
Combat start: "I am here. Chaos will echo from these walls. You will face me now, Character. Prepare yourself."
At 75% Life: "Well now. Nicely executed move. Is there more?"
At 50% Life: "There now! That is more like it!"
At 25% Life: "So the battle has turned, has it?"
Defeated: "My compliments on your victory."
Defeats a villain: "What a pity. Recluse's faith was misplaced."
- Calamity Arachnos profile for a list of his powers.