purity acts like the multiplier for powersources basically.
Quote:
**Note that for powersources, you divide the stats of that PS by the 'purity' of the armor piece . example: a powesource that gives +150 mana would give a piece of armor with 50 purity +75 mana . (150 * 0.50=75)
The main difference between the misty & transluscent powersources is that the transluscent sources have stronger procs. For a table on the stats of Powersources (at 50% purity) check this page out: http://www.eqwiki.net/wiki/Combine_Power_Sources
so if you put a 20 purity aug on a piece of armor that has say 50 purity, the piece of armor then has 70 purity, thereby increases the amount of power it "draws" from the equipped powersource.
powersources are like battaries and drain , and you have to buy new ones constantly. Having more purity does not cause them to drain faster though, but the downside is that if a player does not like using or buying powersources often, these augs are worthless.
also, these augs only fit in type 13 slots (energeiac armor), so don't buy them if you don't have any type 13 slots. I myself think these augs are way overpriced, for how limited their use is. My casters have full sets of praetorian armor, but i get tired of equipping and unequipping the powersources constantly in order to stop them from draining. I only use them on very intense raids or groups, so spending the orux on the augs just isn't worth it to me
the new patch will make it so that even if you have the powersource equipped, then it will not drain power. Only if you are in attack mode will it drain power, so you don't have to unequip it.