1. Armour from the Temple of Naga
2. Horn from the Crypt
3. Shield from the Shadow Ruins
I still need:
Weapon from the Daedroth Castle--where is this castle located?
Ring from the Maze of Irythanbl, which I know I cannot go to until I have the 4th Relic.
To be honest, I think you are confused. If you got a shield from the Shadow Ruins then you did not get a Relic of Power. The relic that you get from the Shadow Ruins is the Rod of Divinity. The Shield of Retribution is obtained from the Draedoth Temple, which is located in the Vale of Ruin.