From Halopedia, the Halo wiki
Craig Mullins is an artist and painter. He worked on Halo: Combat Evolved as a matte and concept artist, having previously worked on art for Bungie's Marathon game series. He worked closely with other artists, such as Shi Kai Wang, to produce the concept art for the landscapes of Halo, the architecture of the UNSC Pillar of Autumn and the Truth and Reconciliation, and he helped design the appearance and culture of the creatures of the Covenant, and even some of the weapons.
He also created the cover artwork of the Halo Encyclopedia.