An ongoing downside to a wide range of games is always that as new levels, gear, and dungeons are let go, the older ones learn to lose their value. The Cheap Tera Gold they drop won't be viable to use, and so they have hardly any utility for players which might be looking to progress throughout the game and have prepared for such things as end-game PvP, dungeons, and raiding. After all, the important reason for doing dungeons is always to work on convalescing items through drops and currencies.
Through this refresh, TERA is breathing new life back into those two dungeons, helping repurpose them somewhat for the community to get familiar with, enjoy, and obtain some advantages from once more. This is especially best for those who have never taken part in either in the other versions, so it helps show that new content can nevertheless be created through the base from the old. These dungeons are likely to be more challenging than their older counterparts, too, so even when you have run them soon you can do them your eyes closed, there exists still likely to be a Tera PC Items challenge awaiting.
