An Apothecary is a specialist Firstborn and Primaris Space Marine medicae officer who possesses advanced biomedical and scientific training and who serves as a combat medic and research physician for his Chapter. An Apothecary's role in battle is to recover the gene-seed from slain Astartes and to tend to the wounded and maimed.

The Apothecary must be as courageous as his fellow Space Marines if not more so, for he must perform his life-saving surgeries in the midst of the battlefield. If a Space Marine is injured, the Apothecary will use his medi-pack, called the Narthecium, to tend to the wounds. 

Nartheciums can dispense medical aid and perform complex surgery -- cauterising, stitching, removing shrapnel, and more. Even severely injured Space Marines can fight again with the aid of the Narthecium.