Abomination

The necromantic construct was animated using an experimental mix of divine, arcane, and planar energy. 
Cassius AlbirioConred, two necromancers aligned with Tidal Wave and the Cult of Shan'ach, created the construct as an experimental weapon to unleash it upon Ashtorian ships in the harbor.
The Abomination was extremely resilient and strong and could fire very dangerous beams of black light.
You managed to destroy it in a final fight in the sewers under the city.