Imp's Cold Sweat is the last stage in Stories of Legend sub-chapter 20, Silk Road.
After the Boss appears
Since Sunfish Jones outranges all Normal/Special Cat Units, and has a 30% chance to slow any cats hit with his attacks, the best way to win this is using short ranged Cats and luck. Both types of Titan Cat are useful because they can survive multiple hits.
Ramen cat will help a lot, as it takes only 1/4 damage from Angels and is quite tanky for its cost.