It's designed to fit all 98 miniatures plus a separate module for the Witch-King of Angmar middle cilinder, since the figure needs to be connected directly to the base to fit in the box (I put it on module 01-01-02).
The modules fit in the bases with rails and the floors with magnets (3 x 2 mm):
https://www.amazon.es/gp/product/B003BKPIN0/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
The author hasn't provided the model origin yet.