The Day of Ascension is an event spoken of by the Tal'darim who worship Amon. It is said that on this day, the cycle of the xel'naga will end, and the Tal'darim will ascend. After his resurrection during the Second Great War, Amon decreed that the day was close at hand. According to Nuroka however, the day will never come. That Tal'darim who perish in Rak'Shir duels are the ones who truly "ascend" in Amon's eyes.
"Serve me and rule. On the Day of Ascension, the corrupted cycle will end. On the Day of Ascension, you will rise beyond any master."