After the geth secure a location, they round up and impale dead and living bodies on mechanical spikes. The spikes rapidly transform these victims into withered husks, extracting water and trace minerals and replacing them with cybernetics.
The cybernetics re-animate the lifeless flesh and tissue, transforming the bodies into mindless killing machines. Some Alliance soldiers refer to the husk-generating spikes as Dragon's Teeth, a reference to the mythological berserkers who sprang up from the earth wherever the teeth of the dragon Ares were planted.
Dragon's Teeth and husks bear little resemblance to other pieces of geth technology. No one is sure why a synthetic race would bother to drain the miniscule amount of recoverable resources from organic corpses, though the value of reusing them as shock troops is obvious.