A hemalurgic spike works by stealing the little bit of Preservation within a person's soul and splicing it into another's, granting specific abilities depending on the abilities of the sacrifice and the placement in the recipient. Since the ability to use allomancy is directly proportional to the amount of Preservation in one's soul, no matter how it got there, and the inborn level of Preservation in a person is a function of their parents levels at the time of conceiving, the children of Inquisitors would be almost guaranteed some allomantic ability, and possibly feruchemical ability as well. That is assuming, of course, that Inquisitors breed true, after all, we only know of one hemalurgic creation that breeds true, the Kandra, and even they don't breed completely true. Given this I believe that the number of spikes effects the ability to reproduce, the more spikes a creature posses the less likely it is to breed true but we will need to meet more hemalurgic creations to confirm this as right now we only have three: 1) Kandra with two spikes who breed somewhat true, Mistwraiths as opposed to Kandra, 2) Koloss with four spikes and don't breed true and, 3) Inquisitors with eleven plus spikes and probably don't breed true.
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fixed a small spelling mistake