In order to make this stone you must have an Alchemist Stone already as an ingredient to make the Redeemer's Stone.

You will need to be Exalted to buy the recipe.
Mats are:
1x Alchemist Stone
6x Primal Life
2x Nether Vortex

The effect won't stack but they are both unique, not unique-equipped, so it may be possible to make the Alchemist Stone again and equip both Stones.