Unowned relics of different tiers don't appear in the relics tabs.
In the champions tabs you can see which champions you have at different tiers (7/6/5/4/3/2/1*s) but that is not the case for relics. If you use the filter to select only one of these tiers you can see which you don't have (these are grayed out) and which ones you do have.
For example, I don't have a 4* storm relic but I can't see the grayed out profile of this relic if I only select 4* relics from the filter because I have a 3* storm relic. Obviously this makes things a little confusing and while it looks like I have all relics in the game the truth is that It's combining all my 3/4/ and 5* relics.
This also doesn't allow you to see the abilities of relics you don't have. So I can't see the abilities of a 4/5/6* storm relic because I have a 3*