My understanding of nicrosil is that you must supply the investiture you wish to store . If you want to store allomancy you have to burn the metal and then siphon the investiture into the metalmind rather than using it . I ' m not completely clear on this though so maybe someone else can confirmdeny ? You can increase your allomancy this way . Remember how Marasi was able to push off trace metals in the Earth at the end of BoM ? The impression I get is that the faster you tap the metalmind the more powerful your allomancy is . I ' d imagine that in theory tapping someone else ' s identity metalmind would allow you to take on their identity so you could use their other metalminds . In practise I ' m not sure how you produce an identityless identity metalmind that other people can tap in the first place .