All hail the magical bird-god! Some time ago, a large portion of chaos followers came into my possession (and the space-elves flew off elsewhere). Amid the pile of random plastic and metal was this hefty pewter monstrosity.
My chaos lord, Tzaanateclis, was very keen to have a hellcannon in his possession so he took his horde into the frozen wastes to seek out the chaos dwarves. He met them upon the field of battle and as he emerged victorious he demanded a hellcannon made.
The daemon Gustius was summoned and bound by the dwarves' fell magiks, at the cost of many more lives. Gustius, and a crew of chaos dwarf engeneers, was gifted to Lord Tzaanateclis. Appeased, the horde moved on to seek more battles.
Gustius was painted similar to the rest of the horde, with blues and gold. Black was used on the majority of the metal to make the steel show brighter. The steel was also done different to the usual way; boltgun metal, devlan mud wash (lower areas) and thrakka green (upper surfaces).
The flames and skulls were originally going to glowing blue, then I thought that adding some green would look good after scrolling through blogger. It turned out well, I think.
Of course, no artillery/monster would be complete without the crew, and face it, chaos dwarves are awesome!