Lias Issodon is the Chapter Master of the Raptors Chapter of the Adeptus Astartes.
Read more about his backstory on the Lexicanum
I use Lias as the leader of my force in most of the games where I field my Raptor army.
He does not have an official model from Games Workshop, or from Forgeworld.
In my games he is most often represented by this model:
It is built from the one of the models in the Forgeworld Legion Recon Squad kit and is painted in the Raptors Colour scheme from the Badab War.