Spawns a Trapdoor in each shop that leads to an additional underground shop that can sell 2-5 of the following:
A Trinket for 15 cents.
An Item for 15-30 cents. Items will be from the Secret Room, Shop, Devil/Angel Room, or Boss Room items; there can be multiple items from different item pools, but items will stay to their chosen item pool if rerolled.
Devil/Angel room items can cost up to 50 cents, and Secret Room items can cost up to 99 cents.