In 9.1.5 they buffed the mobs inside the Rift in Korthia, they now drop
Relic Fragments too! However most of them has quite poor droprate except the big elites called
Famished Darkness. These has a similar loot table to rares in Korthia... The only difference is that they are much easier to farm, since there are a lot of them.
Their numbers are especially large in the Maw, which most people might not think about. You are also able to skip the root NPCs completely!
Depending on your Archivist's tier, they will drop different amount of relics. However at tier 5 you quite often see 3-4
Perplexing Rune-Cubes or
Tattered Fae Designs, granting 150 research each...
Also keep in mind you need to be tier 4 to be able to keep buying the
Repaired Riftkeys, but it goes quite fast these days to reach 4, also the rares in Korthia has quite a solid key droprate
By forming a party of 5, I was able to grind about 9250 reputation in 1 hour and 5 minutes, by maximizing the route and RNG, you can definitely reach 10k reputation an hour without too much trouble...
The most important is that you are early to grind it, before more people figure it out and starts to farm the Darkness!