is it possible to create your own unique attribute for an item?
like
+0.33% frostburn damage per 1 spirit
Not that I know of. 
ok, what about creating a drawback/negative stat??
like
reduced energy/energy regen by 60%
Should be do-able.
how in DRB editor?
the attribute is applied to my char not on the enemy btw
none?
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a way to change the color of the items background?
a way to change the items rarity name?
adding a new color other than the default given in http://www.grimdawn.com/forums/showthread.php?t=46631