Mardonis was aboard the Spear of Adun during its first flight, and informed the grand preservers of the creation of two more arkships. He asked their council as to how many more the Protoss Empire should make, to which they were forced to deliberate.
Years later, Mardonis was on the council that heard the grand preservers' decision. They decided that the arkships should be buried for a time when the protoss would need them the most, that no more should be constructed, and that both a cadre of warriors and grand preservers should be buried with them. Mardonis allowed this to go through.