How To Get The Most Renegades Coins

Where are you guys finding these mystic artifacts? The event wording is confusing.

You get them randomly when picking up normal artifacts from monsters, providing you have empty etc space. Once you pick one up, you get an event quest on the left side of the screen.

I've gotten 3 so far, and i'm at around 500 points, so they aren't all that rare. If you get one, do the quest straight away before hunting more because i'm pretty sure you can't find another if you already have one in your inventory. (Does anyone know for certain?)