Hmm, I’m not sure exactly, but from Googling it, it looks as though it comes from a Jennerit Loot pack, perhaps?
If you don’t have Voxis Core, just use anything that will increase your Skill Damage, or perhaps increase your survivability. Cooldown would also be good, so that you can use your other abilities more often as well.
Also, if you’re not already doing so, I’d recommend using the helix upgrade that adds Stun to your Arc Mines.
(But, keep in mind, this is advice coming from someone who only really played as Toby in PvP to complete the lore challenge and who immediately stopped playing as Toby in PvP as soon as he was done with the challenge! : P ie. He’s not my best character and there are those out there who may have better advice. That being said, if you’re in the same boat as I was, this may be just what you’re looking for).