Wonder what ring could be... WAIT

XMV-HXX-KTS You get a RoW +2 early on, but the imp has a +4 RoW, so you could achieve a +21 RoW with the possibility of transmutation if you wish. There's also a ring of haste +1 early on and the wandmaker has a +2 wand of frosting and something else. The only plate armor I could find in THE WHOLE DUNGEON was the one sold by the imp. Might've missed one on the fall pit empty well rooms though. The ring on the second shop is a RoArcana, as you might deduce from the pictures.