frost / white powder or cream spread over a surface / frosting / (skin) cream
霜
=
相
+
雨
:
The ent (相) wants to eat Sheldon Shrimp (shu) in front of the anglepod (ang1), and before he devours him he adds frosting (霜) to Sheldon's shell. Unfortunately it starts to rain (雨) and the whole frosting is washed off.