Battle Group Iolus is part of Indomitus Crusade Fleet Tertius and it has gone through two iterations so far, during the course of the Crusade.[1b]
History
The first iteration was led by Groupmaster Dionis in the early years of the Indomitus Crusade. Among the battles it took part in under Dionis' command[1a] was the battle for Lessira. While Indomitus Crusade Fleet Quintus had originally targeted the former world for reconquest, Tertius's ambitious Fleetmaster, VanLeskus, sought to beat them to it. Doing so would increase her standing within the Crusade and so VanLeskus ordered several of Tertius' Battle Groups to race to Lessira. Iolus was among them, but while they later succeeded in conquering the world before Fleet Quintus arrived, half of the Battle Group's capital warships were destroyed in the battle. Battle Group Iolus would then continue fighting in the Indomitus Crusade, but it had suffered a deadly wounding at Lessira which it did not recover from. This caused Iolus to begin to unravel and allowed Tertius Groupmaster Eloise Athagey's Battle Group Saint Aster to rise in prestige.[1c]
The two Battle Groups would later be among the Crusade's forces, that defended Segmentum Solar from attacks by the Word Bearers Traitor Legion. This brought about the end for Dionis' command, though, as Iolus fought to defend the Imperial world Xeriphis, from the Word Bearers. Despite Dionis' efforts, the Traitor Legion went on to overwhelm Iolus' fleet and practically destroyed the Battle Group. Dionis was among those who were killed and the remnants of Iolus were then merged with Groupmaster Eloise Athagey's Battle Group Saint Aster[1a]. She would then take command of the new Battle Group, but to her dismay it would retain the name of Iolus. All the prestige and victories Athagey had led Saint Aster to was now finished, as it was submerged under Iolus' recent failure. While Athagey would lead the second iteration of Iolus to victory at Xeriphis, and has gone on to claim further victories since then, the loss of Battle Group Saint Aster still deeply angers her.[1b]
During the Battle at Paradyce II in the Pariah Crusade, Battle Group Iolus, Fleet Tertius was largely destroyed by a massive Necron fleet. The disaster saw the deaths of both Fleetmaster VanLeskus and the capture of Groupmaster Athagey, though a portion of the fleet was able to escape thanks to their efforts.[2a][2b]