My understanding is that there are 8 base metals, giving various abilities; and their alloys, giving a generally opposite ability.These 16 metals can each be alloyed with Atium for some temporal effect much like with pure Atium. Each of these 33 metals has their own type of Misting. Lerasium permanently adds to the Preservation of an ingester (beyond one threshold making one a Misting[type determined by genetics] and beyond another a Mistborn); It can be alloyed with any of the other 33 metals to focus the Preservation added exclusively to a given metal, creating a misting of that alloyed metal (a full tablet of Preservation that focused would yield a ludicrous level of power; at least savant level, without the drawbacks and with the ability to become a savant on top of that[the availability of enhancement metals must be remembered as well:P] for that metal{ie. when given a set quantity of Larasium becoming Mistbon may not be the be all and end all}). This totals 67 metals and a very fun magic system.