1. go Past Bichon Weapons NPC (there are 2 of them talk to Charsi, holding weapon you click on NPC and get info about quest items you need +weapon to proceed on 1st upgrade
You need to gather Fire and Darkgem chips (PB mobs drop them) merged til you make 1 Large each (thats 27 chips each one) +OmaLordSpiritStone +weapon for 1st upgrade.
2. holding upgraded weapon NPC gives you info about quest ietms you need to gather for 2nd upgrade
You need to gather Fire and Darkgem chips merged til you make 3 Large each (thats 81 chips each one) +EvilMirFlame +weapon for 2nd upgrade.
3. CONGRATULATIONS YOU HAVE A FULL UPGRADED EvilMirWeapon!!!
P.S. Every upgrade adds some stats on weapon ONTOP of those it already have, PLUS gains 2 lvls required to use each upgrade.
Xarris and tsirki.