While playing as a Freerunner, I acquired a second Ring of Shadows +1. Naturally, having an open slot, I equipped it. Now, does Pixel Dungeon only read the highest of the two rings or does it add the two upgrade levels together?
According to the wiki, It depends on the type of ring. In the case of the Ring of Shadows, the bonuses will stack.
When two rings of the same type are equipped, the rings’ levels simply add up, except for ring of Detection, Elements, Haggler, Herbalism, Power and Thorns.