the only mode you can get extra piety is crafthing accesoryes (for now, meaby change in the expansión), but the fact is the drk have the same vit like a paladin, ¿so the dark knight can expend some vit for extra mp?, and the ppl how play with drk say in 3 use you out of mp, and in the live letter letter you can see a drk lvl sinc to 54 with 3300 of mp, asuming this guys play the drk in lvl 60 and se say only have 3 use of the dark arts, meaby aprox of 5k-6k of mp in lvl 60, you need a huge amount of piety to get another use of dark arts, thats means sacrifyce some vit and other stats and put in the relic full piety and meaby can get another use.

man bis in drk gonna be a maddnes.