The new SpyDroid assigned to follow subject followed him from Steel Canyon into the Sewer Network, down through the Abandoned Sewer Network to the centre (known as the Underworld) and watched as he entered a keycode to open a security door. Inside it found a large Rikti operation in a tunnel heading vertically down. At the bottom it found the abomination seen in the image.
In the tunnel Solos and the other members of his team found strange guns (presumably originating from the Rikti homeworld). Unfortunately when activated, energy from the guns short circuited the SpyDroid so it is un known what happened during the battle.
A security camera in Steel Canyon captured the group an hour later however, so it is presumed the Hydra was destroyed.