Tarsis Ultra System

The Tarsis Ultra System is an Ultima agri well that took Guilliman's name after he saved a local soldier in the Great Crusade, then became a Leviathan battleground in 999.M41. Uriel Ventris, the Mortifactors, and Inquisitor Kryptman broke a tendril here.

The Iron Warrior Honsou wrecked the victory by firing a stolen virus into leftover Tyranid flora; the growth ate the air, and the agri-world died as a scoured rock. Sister worlds Barbarus Prime, Chordelis, Parosa, and Yulan share the well. Barbarus Prime here is a Tarsis neighbour, not Mortarion's homeworld.

The Tarsis Ultra System still matters as the victory Honsou unmade. Unofficial fan notes keep the Ultima parent and refuse to confuse Barbarus Prime with Barbarus.