During Painted Dome, after Kaveh's Normal, Charged, or Plunging Attacks hit opponents, his Elemental Mastery will increase by 25. This effect can be triggered once every 0.1s. Max 4 stacks. This effect will be canceled when Painted Dome's effects end.
If you have mistsplitter or Futsu then I'd recommend going for C1, C1 is generally probably better ...