How To Get The 1 Decrepit Sewers Key

So I did the sewers quest and got the dungeon key I failed the dungeon and now I don't know how to get the key back h e l p

 

find a key guardian that looks like a skeleton that spawns around ragni and the nivla forest

 

Dungeon key guardians, which generally spawn near the dungeon or in similar level-ranged areas, drop a dungeon key upon death. The Decrepit Sewers Key Guardian looks like an armored skeleton, and has four phases - killing the third phase drops the key, since the fourth phase is a passive move that runs away. They're quite common along the Emerald Trail, and outside the north gate of Ragni (near the dungeon itself).

 

Where do I find the emerald trail again?

 

its the road to the nivla forest from rangi

 

A further clarification: The road that runs East out of Ragni to the nivla forest