Evil ice-metal is a hell of a drug, as evidenced by this handsome Xardorok Sunblight fella and his frosty robo-dragon.
I've included two phase stat blocks for king grump representing his aspects as a warlock of Asmodeus and as a dwarven super-mutant; you should be good to use just one of them if your players hit Sunblight at the recommended level, but if you've got a large party or they get overleveled, you've got this phase 2 to pull out of your back pocket.
For the chardalyn dragons, likewise, there's a second version to drop in if your players are going to piece up the lower CR one.