The Cube can only be found in Adventure mode. There is no long quest or list of requirements to find it. Simply talk to Zoltun Kulle in Act town and then travel to the The Ruins of Sescheron in Act 3 and find the Elder Sanctum, somewhere on that map you will find the cube.
Subsequently, question is, where can I buy westmarch holy water? The Westmarch Holy Water is a crafting material in Diablo III, added in Patch 2.3. 0. It is only used with Kanais Cube for various recipes and by for legendary and set items crafted by Blacksmith. This material is obtained from a Horadric Cache given by Tyrael for completion of Act V bounties in Adventure Mode.
Secondly, can you augment primal ancients?
To augment an Ancient or Primal Ancient weapon, a Legendary Gem of Rank 30 or higher is required. Augmenting an Ancient or Primal Ancient Ring or Amulet requires a Legendary Gem of Rank 40 or higher, while augmenting an Ancient or Primal Ancient piece of armor requires a Legendary Gem of Rank 50 or higher.
Where does Ramaladnis gift drop?
It drops randomly from any target on Torment 1 or higher, but the drop rate is not boosted by Magic Find, its mot more commonly found from in Rifts or out of them, doesnt drop specially from Guardians or Act Bosses, etc.