According to the historical records that had been passed down by senior big shots, a normal Ninth Stage heavenly tribulation would consist of three separate tribulations.
The first tribulation, Transcending Mortality, allowed a Profound Sage to give birth to a Tribulation Transcender's Vitality within their body.
The second tribulation allowed a Profound Sage to create a 'Tribulation Bone' within their body, which would, in turn, give them the ability to shuttle through space.