Temple Hose +1  

This is a quest not a synthesis as it will never break. sahgareeha(or something like that) in port jeuno is the npc that deals with limbus and artifact upgrades.
she will tell you what you need to upgrade pieces of artifact armor, under armor upgrades if i remember rightly. ofcourse the fact you need access to limbus to gain 2 of the 5 items required goes without saying. but i said it anyway in case
a newer player is reading this post.

hope that helped.

The ingredients are:

25 Ancient Beastcoins (drops in limbus)
1 Ancient Brass (rare/ex, drops in Limbus Apollyon)
1 Utopian Gold Thread (rare/ex, drops in Limbus Temenos)
1 Manticore Leather (synthed)
1 Temple Hose

Just traded my stuff in today for this. Extra point of MND for my Chi Blast gear and I can get rid of those hume Custom Slacks ^^