The Photep is known to have transported the Thousand Sons contingent to the Triumph of Ullanor, where Horus was elevated to the esteemed rank of Warmaster by the Emperor himself, in recognition of his numerous great deeds and outstanding leadership throughout the Great Crusade. This flagship also transported the Thousand Sons to the historic Council of Nikaea, to determine once and for all whether the use of psychic abilities within the Space Marine Legions should be allowed. Magnus was aboard the Photep when he experienced a revelation in regards to the inevitable destruction of his homeworld of Prospero at the hands of the Space Wolves Legion.