Artemas bow

reneco11

My bow is lvl 80, how can I increase the lvl. Thought I read something about some kind of oil or something like that. I need to but 3 of them. I just don't know where or how the process works.

Thunder073

You need to do the ATMAS. Also there is oil/items you need to buy that are located right near initial legendary quest NPC. about 5 steps to the left of him. The firepit thingy

Dr_Shivinski

The item the OP is referring to is the Thanravian Mist (mispelled but you will know what I mean) you need 3 of from the Vendor in Mor Dhona. She is the Soldiery/Poetics vendor, search through her goods too see how much soldiery you need to purchase the 3 mists. 

After obtaining the mist you go to Hyrstmill in North Shroud (I suggest teleporting to Gridania and using the Aetheryte from there to the North Shroud, it will put you much closer to Hyrstmill than teleporting directly to North Shroud.) 

After that, check out this guide here for the rest of the steps to the long and arduous process of upgrading your relic weapon.