Ryza

Ryza is the plasma forge: Executioners, Stormblades, and a priesthood that treats every battle as a weapons test. It was second only to Mars at the end of the Crusade and paid for that in the Heresy. Two Ork Waaaghs and a daemon invasion have since chewed the dunes. Some older armour books park it in Segmentum Solar; the working map keeps it in Ultima, just east of Terra.