The Epic of Alexander (Ultimate) was added in patch 5.11 of the Shadowbringers expansion.
The Epic of Alexander (Ultimate) becomes available at level 80 as part of the “Nor Any Drop to Drink” quest, which is given by Wandering Minstrel – Kugane (X:11 Y:12).
The raid has a minimum ilevel of 0 to enter and rewards you with:
Allagan Tomestone of Poetics: 100