Merek Grimaldus, the Hero of Helsreach, is the High Chaplain of the Black Templars Space Marine Chapter. Grimaldus is also a noted veteran of the Third War for Armageddon. During the Battle for Hive Helsreach, Grimaldus led the defence of the Temple of the Emperor Ascendant, which had stood since Armageddon's colonisation. The battle became so heated that the building itself collapsed around the combatants. It was believed that all had perished in the building until Grimaldus, bloody but unbroken, climbed out of the rubble bearing three of the temple's artefacts -- a column from its Major Altar, the Banner of the Emperor Victorious, and holy water from the Stoup of Elucidation. Those Black Templars Apothecaries who examined him later were amazed that Grimaldus had survived, much less found the strength to climb from the ruins. When the war ended, the citizens of Hive Helsreach honoured him with the title of "Hero of Helsreach" and bowed before his passing.

No battle is so bleak that Grimaldus' appearance cannot turn the tide and rekindle the fire in his brothers' hearts. Then, an enemy who thought the battle won will find himself beset once more, smashed asunder by a tide of zealots whose arms have been lent fresh strength, Grimaldus at their head carving another victory for his Emperor.