The back story behind this guy is that he was given Biff Tundrish's geneseed.
That is why he has the spider as heraldry.
When not in terminator armor he is one of the foremost experts on heavy weapons and spends time with every squad when not attached directly to the 1st company just like Tellion does for the scouts.
I really like how the weathering turned out on him.
I used Tamiya weathering powder soot on the exhausts and barrel tip and burnt orange and burnt blue on the assault cannon to mimic heat stress.