Temple of the Emperor Ascendant
From Warhammer 40k - Lexicanum
The Temple of the Emperor Ascendant was a fortified basilica on Armageddon. At the heart of the Hive Helsreach Temple District, it was the oldest temple on the entire world and immortalized the deeds of the colonists who came aboard the Truth's Tenacity.[1a][1c]
During the Third War for Armageddon the temple was destroyed, and a great many relics of the world's first colonists lost. A few were saved by Reclusiarch Grimaldus of the Black Templars, one of only a handful of survivors.[1b][1c]
Trivia
On the Warhammer Community website article showcasing a new Primaris model for Grimaldus, the temple's name is spelled Temple of the Emperor Ascendent.[2]