Another game and another loss, but also another learning experience.
I faced my brother again, he used the same list as before against a heavily tweaked list of mine.
Once again I was able to easily demolish the Custodes, this time with heavy fire from an Exocrine and a trio of Hive Guard. Assassins once again failed to have any severe impact, with the Eversor fluffing horribly while the vindicare spent four turns trying to kill my broodlord.
I almost took out Guilleman himself, tempting him to charge out from his own lines in an attempt to slay one of my hive tyrants. The tyrant survived (barely) by virtue of his invulnerable save and took three wounds off the primarch with one lucky swing. In my following turn I had the tyrant fall back, leaving Guilleman exposed to the same hail of fire that had killed his bodyguards earlier. He survived with two wounds, losing another to a flurry of genestealer strikes before falling back himself.
The game outcome was much like before. Despite my army's vastly improved performance, my swarm simply had far more units to lose. One more game against the forces of Chaos tomorrow, and then I'll begin trying out some necron lists.