Battle for Orar's Sepulchre
The Battle for Orar's Sepulchre was the first battle the entire Ultramarines Chapter would fight in since the First Tyrannic War, and followed from negotiations between the Planetary Governor of Commrath and an Eldar emissary from the Biel-Tan Craftworld. The Eldar requested an ancient artefact from the tomb of an Ultramarines hero, Captain Orar, called the Sceptre of Galaxian. The Planetary Governer refused, and when pleas turned to threats he had the Eldar executed. However, he did not let the warnings go unheard, and asked for the Ultramarines' aid.
Chapter Master Marneus Calgar responded in force. Upon arriving on the planet, he began the fortification of Orar's tomb - though it was already a fairly fortified keep, the Space Marines toppled pillars to use as barricades and steeled themselves for the coming battle.
The Attack Begins
The original attack from the Eldar smashed straight into the tomb complex - and the majority of the Ultramarines forces. Bolter rounds and shuriken fire filled the skies and marines died in their dozens, reaping a rich tally of the foe as they did so. However, the primary assault was stalled and systematically pinned down by the Ultramarine forces. Despite the loss of thousands of Eldar, they could not make any progress towards their target.
Finding the complex to be far harder to take than originally thought, the Eldar proceeded to adopt a more mobile form of warfare. Hundreds of Wave Serpents filled with Eldar attempted to out-manouever the Ultramarine bastion, but Calgar had thought ahead. As the Eldar deployed their troops, they found themselves immediately under fire from Tactical Squads mounted in Rhinos, which would kill the Eldar before returning to their transports and moving to combat more threats. Calgar was instrumental to the continuation of this, co-ordinating these attacks with lethal proficiency while in the midst of the battle. Under the pressure of the seemingly undefeatable defenders, the Eldar began to lose morale.
The Avatar Awakens
The previous attacks, though unsuccessful, had drained the Ultramarines, and fully half the Ultramarines who had begun the battle were dead or wounded. So it was that the third, final attack by the Eldar looked set to overwhelm the defenders.
Spearheaded by an Avatar of Khaine, the attackers regained the will to fight and charged the Ultramarines head on. Under this new onslaught the Ultramarine line buckled, then broke, Eldar spilling through the gap to assault the Space Marines. The Avatar lead the charge, killing dozens of Space Marines with swings of the Wailing Doom. Terminators of the 1st Company engaged the beast head-on, yet their Thunder Hammers and Lightning Claws were completely useless against the foe. It was time for drastic action.
Calgar, knocking enemies flying from the bulk of his armour, engaged the Avatar in single combat. The Avatar swung its sword, which had cut through armour so mercilessly, at the Chapter Master, and all seemed doomed for Calgar. At the last moment, however, Calgar slammed the palm of his hand into the sword and grabbed it with all his strength. The Gauntlets of Ultramar, great relics of the Chapter, buckled and warped, yet held for a brief moment. In that moment, the Avatar was helpless, and Calgar drove his other hand into its molten form. With a deafening roar, the Avatar exploded, leaving Calgar exhausted on the ground. The marines of the Ultramarines Chapter swarmed to surround their Chapter Master, yet no further attack was to come from the Eldar. Following the death of their Avatar, the Eldar broke ranks and fled. The Ultramarines were victorious.
After the battle, Commrath was judged by Calgar to be unfit to defend a relic such as the Galaxian Sceptre, and had it moved to Macragge. This was not a notion that the Planetary Governer refused, and it remained in the Fortress of Hera for the rest of its days.